DA800 User s Manual Real Time Devices, Inc.

Transcription

1 DA800 User s Manual Real Time Devices, Inc. Accessing the Analog World

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3 DA800 User s Manual REAL TIME DEVICES, INC. 820 North University Drive Post Office Box 906 State College, Pennsylvania Phone: (814) FAX: (814)

4 Published by Real Time Devices, Inc. 820 N. University Dr. P.O. Box 906 State College, PA Copyright 1992 by Real Time Devices, Inc. All rights reserved Printed in U.S.A. Rev. A 9311

5 Table of Contents INTRODUCTION... i-1 Digital-to-Analog Conversion... i-3 Digital I/O... i Timer/Counter... i-3 What Comes With Your Board... i-3 Board Accessories... i-4 Using This Manual... i-4 When You Need Help... i-4 CHAPTER 1 BOARD SETTINGS Factory-Configured Switch and Jumper Settings P3 Interrupt Channel Select (Factory Setting: G Connected; Interrupt Channels Disabled) P4 Interrupt Source Select (Factory Setting: EXT) P Timer/Counter Clock Sources (Factory Settings: CLK0-XTAL, CLK1-OUT0, CLK2-OUT1) P7 Through P10 DAC1 Through DAC4 Output Range Select (Factory Setting: -5 to +5 Volts) S1 Base Address (Factory Setting: 300 hex (768 decimal)) S2 and S3 Buffer Bypass Switches (Factory Setting: OPEN (Not Bypassed)) Pull-up/Pull-down Resistors on Digital I/O Lines CHAPTER 2 BOARD INSTALLATION Board Installation External I/O Connections Connecting the Analog Outputs Voltage Outputs Connecting the Analog Outputs 4-20 ma Current Loop Outputs Connecting the Timer/Counters and Digital I/O Running the 800DIAG Diagnostics Program CHAPTER 3 HARDWARE DESCRIPTION D/A Conversion Digital I/O, 8255 Programmable Peripheral Interface Timer/Counters Interrupts CHAPTER 4 BOARD OPERATION AND PROGRAMMING Defining the I/O Map BA + 0: PPI Port A Digital I/O (Read/Write) BA + 1: PPI Port B Digital I/O (Read/Write) BA + 2: PPI Port C Digital I/O (Read/Write) BA + 3: 8255 PPI Control Word (Write Only) BA + 4: D/A Converter 1 LSB (Write Only) BA + 5: D/A Converter 1 MSB (Write Only) BA + 6: D/A Converter 2 LSB (Write Only) BA + 7: D/A Converter 2 MSB (Write Only) BA + 8: D/A Converter 3 LSB (Write Only) BA + 9: D/A Converter 3 MSB (Write Only) BA + 10: D/A Converter 4 LSB (Write Only) BA + 11: D/A Converter 4 MSB (Write Only) i

6 BA + 12: Update DAC Outputs (Write Only) BA + 13: Reserved BA + 14: IRQ Enable (Write Only) BA + 15: Interrupt Status/Clear (Read/Write) BA + 16: 8254 Timer/Counter 0 (Read/Write) BA + 17: 8254 Timer/Counter 1 (Read/Write) BA + 18: 8254 Timer/Counter 2 (Read/Write) BA + 19: 8254 Control Word (Write Only) Programming the DA Clearing and Setting Bits in a Port D/A Conversions Initializing the 8255 PPI Digital I/O Operations Timer/Counters Interrupts What Is an Interrupt? Interrupt Request Lines Programmable Interrupt Controller Interrupt Mask Register (IMR) End-of-Interrupt (EOI) Command What Exactly Happens When an Interrupt Occurs? Using Interrupts in Your Programs Writing an Interrupt Service Routine (ISR) Saving the Startup Interrupt Mask Register (IMR) and Interrupt Vector Restoring the Startup IMR and Interrupt Vector Common Interrupt Mistakes Example Programs C and Pascal Programs BASIC Programs CHAPTER 5 CALIBRATION Required Equipment D/A Calibration X2 Voltage Multiplier ma Current Loop APPENDIX A DA800 SPECIFICATIONS... A-1 APPENDIX B I/O CONNECTOR PIN ASSIGNMENTS... B-1 APPENDIX C COMPONENT DATA SHEETS... C-1 APPENDIX D WARRANTY... D-1 ii

7 LIST OF ILLUSTRATIONS 1-1 Board Layout Showing Factory-Configured Settings Interrupt Channel Select Jumper, P Pulling Down the Interrupt Request Line Interrupt Source Select Jumper, P Timer/Counter Clock Source Jumpers, P Timer/Counter Circuit Block Diagram DAC1 Through DAC8 Output Range Select, P7 Through P Base Address Switch, S Port C Buffer Circuitry Port A Buffer Circuitry Pull-up/Pull-down Resistor Circuitry Adding Pull-ups and Pull-downs to Some Digital I/O Lines P2 and P6 I/O Connector Pin Assignments Voltage Output Connections Current Output Connections, No Loop Supply Current Output Connections, Single Loop Supply Current Output Connections, Multiple Loop Supplies DA800 Block Diagram Timer/Counter Circuit Block Diagram Board Layout ma Current Loop Calibration Connections iii

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9 i-1 INTRODUCTION

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11 The DA800 Advanced Industrial Control series analog output and digital control board turns your IBM PC/XT/AT or compatible into a high-performance testing and control system. Installed within a single short or fullsize expansion slot in the computer, the DA800 board features: 4 fast-settling 12-bit analog output channels, ±5, ±10, 0 to +5, or 0 to +10 volt analog output range, Industrial 4-20 ma current loop source capability, Simultaneous updating of all output channels, 24 TTL/CMOS 8255-based programmable digital I/O lines, Buffered outputs for high driving capability, Three 16-bit, 8 MHz timer/counters, Optional pull-up/pull-down resistors, Simple I/O, strobed I/O & bidirectional I/O operation, Software enabled interrupts (IRQ2-IRQ7), BASIC, Turbo Pascal & Turbo C source code; diagnostics program. The following paragraphs briefly describe the major functions of the board. More detailed discussions of board functions are included in Chapter 3, Hardware Description, and Chapter 4, Board Operation and Programming. The board setup is described in Chapter 1, Board Settings. Digital-to-Analog Conversion The digital-to-analog (D/A) circuitry features two 12-bit converter channels in each AD7237 D/A converter IC for a total of four output channels. The two channels in each AD7237 are internally double buffered and all channels are simultaneously updated by issuing a single command. Each channel can be jumpered to one of four output voltage ranges, ±5, ±10, 0 to +5, or 0 to +10, or configured as a 4-20 ma current loop source. The industrial 4-20 ma current loop signals are less susceptible than voltage signals to electrically induced noise. Digital I/O The DA800 has 24 TTL/CMOS-compatible digital I/O lines which can be directly interfaced with external devices or signals to sense switch closures, trigger digital events, or activate solid-state relays. These lines are provided by the on-board 8255 programmable peripheral interface chip. The 8255 can be operated in one of three modes: Mode 0, simple I/O; Mode 1, strobed I/O; or Mode 2, strobed bidirectional I/O. To ensure high driving capacity, CMOS buffers are installed. These buffers must be bypassed as described in Chapter 1 for Mode 1 and Mode 2 operation. TTL buffers are available on request. Pads for installing and activating pull-up or pull-down resistors on the digital I/O lines are included on the board. Installation procedures are given at the end of Chapter 1, Board Settings Timer/Counter An 8254 programmable interval timer contains three 16-bit, 8 MHz timer/counters to support a wide range of timing and counting functions. The clock, gate, and output pins for each of the timer/counters are available at the P2 I/O connector. What Comes With Your Board You receive the following items in your DA800 package: DA800 interface board Software and diagnostics diskette with BASIC, Turbo Pascal, and Turbo C source code User s manual If any item is missing or damaged, please call Real Time Devices Customer Service Department at (814) If you require service outside the U.S., contact your local distributor. i-3

12 Board Accessories In addition to the items included in your DA800 package, Real Time Devices offers a full line of accessories. Call your local distributor or our main office for more information about these accessories and for help in choosing the best items to support your board s application. Accessories for the DA800 include SIGNAL*MATH acquisition and analysis software, the MR8/MR16 series 8 or 16 channel mechanical relay boards, the OP8/OP16 series 8 or 16 channel optoisolated digital input boards, the OR16 mechanical relay/optoisolated digital I/O board, the TB50 terminal board and XB50 prototype/terminal board for prototype development and easy signal access, and the XT50 twisted pair wire flat ribbon cable assembly for external interfacing. Using This Manual This manual is intended to help you install your new board and get it running quickly, while also providing enough detail about the board and its functions so that you can enjoy maximum use of its features even in the most complex applications. We assume that you already have an understanding of data acquisition principles and that you can customize the example software or write your own applications programs. When You Need Help This manual and the example programs in the software package included with your board provide enough information to properly use all of the board s features. If you have any problems installing or using this board, contact our Technical Support Department, (814) , during regular business hours, eastern standard time or eastern daylight time, or send a FAX requesting assistance to (814) When sending a FAX request, please include your company s name and address, your name, your telephone number, and a brief description of the problem. i-4

13 CHAPTER 1 BOARD SETTINGS The DA800 board has jumper and switch settings you can change if necessary for your application. The board is factoryconfigured as listed and shown on a diagram in the beginning of this chapter. Should you need to change these settings, use these easy-to-follow instructions before you install the board in your computer. Note that by installing resistor packs at four RN locations near the 8255 PPI and soldering a jumper between +5V and common or ground and common in the associated pads for each resistor network, you can configure groups of digital I/O lines to be pulled up or pulled down. This procedure is explained at the end of this chapter. 1-1

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15 Factory-Configured Switch and Jumper Settings Table 1-1 lists the factory settings of the user-configurable jumper and switches on the DA800 board. Figure 1-1 shows the board layout and the locations of the factory-set jumpers. The following paragraphs explain how to change the factory settings. Pay special attention to the setting of S1, the base address switch, to avoid address contention when you first use your board in your system. Switch/ Jumper P3 Table 1-1: Factory Settings Function Controlled Connects the interrupt source selected on P4 to an interrupt channel, IRQ2-IRQ7; pulls tri-state buffer to ground for multiple interrupt applications Factory Settings (Jumpers Installed) All channels disabled; G (ground for buffer) connected P4 Selects the interrupt source EXT P5 P7 P8 P9 P10 Sets the clock sources for the three 8254 timer/counters (TC0-TC2) Configures the output voltage range or current loop settings for DAC1 Configures the output voltage range or current loop settings for DAC2 Configures the output voltage range or current loop settings for DAC3 Configures the output voltage range or current loop settings for DAC4 CLK0-OSC; CLK1-OT0; CLK2-OT1 (all 3 timer/counters cascaded) Jumpers installed on ±5, X1, VEN, VOUT to set output at -5 to +5 volts Jumpers installed on ±5, X1, VEN, VOUT to set output at -5 to +5 volts Jumpers installed on ±5, X1, VEN, VOUT to set output at -5 to +5 volts Jumpers installed on ±5, X1, VEN, VOUT to set output at -5 to +5 volts S1 Sets the base address 300 hex (768 decimal) S2 Bypasses 8255 Port A buffers for Mode 2 operation Open (buffers not bypassed) S3 Bypasses 8255 Port C buffers for Mode 1 or Mode 2 operation Open (buffers not bypassed) 1-3

16 TR5 TR6 TR7 TR8 S1 BASE ADDRESS TR1 TR2 TR3 TR4 5V 5V X1 X2 VEN IEN VOUT IOUT 5V 5V X1 X2 VEN IEN VOUT IOUT Y1 U19 XTAL C7 SWITCH RN1 RN9 P10 P9 AOUT4 AOUT3 C30 C29 C24 RN10 RN7 U20 C18 AOUT2 AOUT1 P7 P8 RN8 U21 82C54 C39 C37 C23 AD7237 AD7237 U17 U19 C41 C35 C36 C25 C42 AD694 U16 U23 AD694 C26 C34 C31 C15 AD712 C16 AD712 C40 C38 C32 C33 C17 AD694 AD694 C27 C28 P2 C19 C5 U5 OSC EC0 OT0 OSC EC1 74LS125 CLK0 CLK1 P5 74HCT08 C6 U15 U6 RN2 PAL 74LS244 P6 U11 C11 74HCT245 PB G PB U18 V V 82C55 PA G U10 PA RN3 U22 C10 74HCT245 SWITCH OT1 OSC EC2 CLK2 U12 RN15 R1 P4 PCL U13 C13 S2 V G PCH PCH RN5 C14 Made in USA C21 + U14 PAL C2 U2 74HCT688 R OT0 OT1 OT2 EXT PC3 PC0 C3 U3 PCL 74HCT138 RN4 V G P3 IRQ G U4 74HCT243 74HCT367 Real Time Devices, Inc. State College, PA C9 C4 U9 S3 C1 SWITCH U1 74HCT245 DA800 U8 74HCT243 + C20 C8 + C43 + C22,,,, Accessing the Analog World Fig. 1-1 Board Layout Showing Factory-Configured Settings P3 Interrupt Channel Select (Factory Setting: G Connected; Interrupt Channels Disabled) This header connector, shown in Figure 1-2, lets you connect an interrupt source selected on P4 to an interrupt channel, IRQ2 through IRQ7. To connect the interrupt source to an interrupt channel, you must install a jumper across the desired IRQ channel. The rightmost pair of pins on P3, labeled G, are provided so that you can install a jumper which connects a 1 kilohm pull-down resistor to the output of a high-impedance tri-state driver which carries the interrupt request signal. This pull-down resistor drives the interrupt request line low whenever interrupts are not active. So, whenever an interrupt request is made, the tri-state buffer is enabled, forcing the output high and causing an interrupt. You can monitor the interrupt status through bit 0 in the status word (I/O address location BA + 15). After the interrupt has been serviced, the clear command returns the IRQ line low, disabling the tri-state buffers, and pulling the output low again. Figure 1-3 shows this circuit. Because the interrupt request line is driven low only by the pull-down resistor, you can have two or more boards which share the same IRQ channel. You can tell which board issued the interrupt request by monitoring each board s IRQ status bit. NOTE: When you use multiple boards that share the same interrupt, only one board should have the G ground jumper installed. The rest should be disconnected. Whenever you operate a single board, the G jumper should be installed. P3 IRQ G Fig. 1-2 Interrupt Channel Select Jumper, P3 1-4

17 INT SOURCE CLK IRQ STATUS INTERRUPT REGISTER +5 V CLR INTERRUPT CLR P3 G Fig. 1-3 Pulling Down the Interrupt Request Line P4 Interrupt Source Select (Factory Setting: EXT) This header connector, shown in Figure 1-4, lets you connect one of six interrupt sources for interrupt generation. These sources are: OT0, OT1, and OT2, which are the three 8254 timer/counter outputs; PC3, which is the INTRA signal from the 8255 PPI; PC0, which is the INTRB signal from the 8255 PPI; and EXT, an external interrupt you can route onto the board through the P2 I/O connector. To connect an interrupt source, place the jumper across the desired set of pins. Note that only ONE interrupt source can be activated at a time. P4 OT0 OT1 OT2 EXT PC3 PC0 Fig. 1-4 Interrupt Source Select Jumper, P4 P Timer/Counter Clock Sources (Factory Settings: CLK0-XTAL, CLK1-OUT0, CLK2-OUT1) This header connector, shown in Figure 1-5, lets you select the clock sources for the 8254 timer/counters, TC0, TC1, and TC2. The factory setting cascades all three timer/counters, with the clock source for TC0 being the onboard 8 MHz oscillator, the output of TC0 providing the clock for TC1, and the output of TC1 providing the clock for TC2. You can connect any or all of the sources to an external clock input through the P2 I/O connector, or you can set TC1 and TC2 to be clocked by the 8 MHz oscillator. Figure 1-6 shows a block diagram of the timer/counter circuitry to help you with these connections. NOTE: When installing jumpers on this header, make sure that only one jumper is installed in each group of two or three CLK pins. OSC EC0 OT0 OSC EC1 OT1 OSC EC2 1-5 CLK0 CLK1 CLK2 Fig Timer/Counter Clock Source Jumpers, P5 P5

18 8254 P5 800 I/O CONNECTOR P2 TIMER/ COUNTER 0 CLK GATE CLK0 OSC (8 MHz) +5 V PIN 39 PIN 19 EXT CLK 0 EXT GATE 0 OUT PIN 40 T/C OUT 0 OUT0 CLK1 TIMER/ COUNTER 1 CLK GATE +5 V PIN 43 PIN 41 EXT CLK 1 EXT GATE 1 OUT PIN 42 T/C OUT 1 OUT1 CLK2 TIMER/ COUNTER 2 CLK GATE +5 V PIN 45 PIN 46 EXT CLK 2 EXT GATE 2 OUT PIN 44 T/C OUT 2 Fig Timer/Counter Circuit Block Diagram P7 Through P10 DAC1 Through DAC4 Output Range Select (Factory Setting: -5 to +5 Volts) These identical header connectors, shown in Figure 1-7, let you independently set the output of each D/A converter to one of four voltage ranges or as a 4-20 ma current loop source. Figure 1-7 shows all five possible configurations for these headers, and the table below summarizes these settings. The topmost pair of pins, 5V, is jumpered when operating in a unipolar voltage range or as a current loop. The next pair of pins, ±5V, is jumpered when operating in a bipolar voltage range (±5 or ±10 volts). The X1 and X2 pins set the range multiplier. When a jumper is installed across X1, the multiplier is set at times 1 for 0 to +5 and ±5 volt ranges. When the jumper is installed across X2, the multiplier is times 2 for 0 to +10 and ±10 volt ranges. The VEN pins enable voltage outputs when a jumper is installed, or the IEN pins enable 4-20 ma current loop operation when a jumper is installed. Finally, a jumper must be placed across the VO pins for output voltages or across the IO pins for 4-20 ma current loop operation. To configure each header for your application, install the jumpers as shown in the diagrams on the next page for the desired output range. The factory setting of each DAC is shown in Figure 1-7a, ±5 volts. Jumpers (left to right) Output Range ±5V 0 to +5V ±10V 0 to +10V 4-20 ma 5V OFF ON OFF ON OFF ±5V ON OFF ON OFF ON X1 ON ON OFF OFF ON X2 OFF OFF ON ON OFF VEN ON ON ON ON OFF IEN OFF OFF OFF OFF ON VOUT ON ON ON ON OFF IOUT OFF OFF OFF OFF ON 1-6

19 5V ±5V X1 X2 VEN IEN VOUT IOUT Fig. 1-7a ±5V Output 5V ±5V X1 X2 VEN IEN VOUT IOUT 5V ±5V X1 X2 VEN IEN VOUT IOUT 5V ±5V X1 X2 VEN IEN VOUT IOUT 5V ±5V X1 X2 VEN IEN VOUT IOUT Fig. 1-7b 0 to +5V Output Fig. 1-7c ±10V Output Fig. 1-7d 0 to +10V Output Fig. 1-7e 4-20 ma Output Fig. 1-7 DAC1 Through DAC4 Output Range Select, P7 Through P10 S1 Base Address (Factory Setting: 300 hex (768 decimal)) One of the most common causes of failure when you are first trying your board is address contention. Some of your computer s I/O space is already occupied by internal I/O and other peripherals. When the DA800 board attempts to use I/O address locations already used by another device, contention results and the board does not work. To avoid this problem, the DA800 has an easily accessible DIP switch, S1, which lets you select any one of 16 starting addresses in the computer s I/O. Should the factory setting of 300 hex (768 decimal) be unsuitable for your system, you can select a different base address simply by setting the switches to any value shown in Table 1-2. The table shows the switch settings and their corresponding decimal and hexadecimal (in parentheses) values. Make sure that you verify the order of the switch numbers on the switch (1 through 4) before setting them. When the switches are pulled forward, they are OPEN, or set to logic 1, as labeled on the DIP switch package. When you set the base address for your board, record the value in the table inside the back cover. Figure 1-8 shows the DIP switch set for a base address of 300 hex (768 decimal). Base Address Decimal / (Hex) Table 1-2: Base Address Switch Settings, S1 Switch Setting Base Address Decimal / (Hex) Switch Setting / (200) / (300) / (220) / (320) / (240) / (340) / (260) / (360) / (280) / (380) / (2A0) / (3A0) / (2C0) / (3C0) / (2E0) / (3E0) = closed, 1 = open 1-7

20 Fig. 1-8 Base Address Switch, S1 S2 and S3 Buffer Bypass Switches (Factory Setting: OPEN (Not Bypassed)) Mode 1 Operation (S3) When operating the 8255 in Mode 1, the lines of Port C function as control lines, some as outputs and some as inputs. When using Mode 1, the Port C buffers must be removed and bypassed to allow the Port C lines to be individually set as inputs or outputs. Figure 1-9 shows the Port C buffers, and the following steps tell you how to configure the board for Mode 1 operation. To remove buffering from Port C: 1. Close DIP switches 1 through 8 on S3. 2. Remove U8 from the board. 3. Remove U9 from the board. CAUTION: Remember, whenever you close the switches on S3, be sure to remove the buffers, U8 and U9, from the board. Failure to do so may damage the board. Mode 2 Operation (S2, S3) When operating the 8255 in Mode 2, the lines of Port A must be bidirectional and the lines of Port C function as control lines, some as outputs and some as inputs. When using Mode 2, both the Port A and Port C buffers must be removed and bypassed. Figure 1-10 shows the Port A buffers, Figure 1-9 shows the Port C buffers, and the following steps tell you how to configure the board for Mode 2 operation. To remove buffering from Ports A and C: 1. Close DIP switches 1 through 8 on S2 (Port A). 2. Remove U10 from the board. 3. Close DIP switches 1 through 8 on S3 (Port C). 4. Remove U8 from the board. 5. Remove U9 from the board. CAUTION: Remember, whenever you close the switches on S2 and S3, be sure to remove the buffers, U8, U9, and U10, from the board. Failure to do so may damage the board. 1-8

21 82C I/O CONNECTOR P2 / P6 PC7 PIN 24 PIN 16 PORT C PC6 PC5 PC4 PC3 BUFFER U8 PIN 26 PIN 14 PIN 28 PIN 12 PIN 30 PIN 10 PIN 32 PIN 8 PC2 PC1 PC0 BUFFER U9 PIN 34 PIN 6 PIN 36 PIN 4 PIN 38 PIN 2 S Fig. 1-9 Port C Buffer Circuitry 82C I/O CONNECTOR P2 PA7 PIN 23 PA6 PIN 25 PA5 PIN 27 PORT A PA4 PA3 BUFFER U10 PIN 29 PIN 31 PA2 PIN 33 PA1 PIN 35 PA0 PIN 37 S Fig Port A Buffer Circuitry 1-9

22 Pull-up/Pull-down Resistors on Digital I/O Lines The 8255 programmable peripheral interface provides 24 parallel TTL/CMOS compatible digital I/O lines which can be interfaced with external devices. The lines are divided into four groups: eight Port A lines, eight Port B lines, four Port C Lower lines, and four Port C Upper lines. You can install and connect pull-up or pull-down resistors for any or all of these four groups of lines. You may want to pull lines up for connection to switches. This will pull the line high when the switch is disconnected. Or, you may want to pull down lines connected to relays which control turning motors on and off. These motors turn on when the digital lines controlling them are high. Pulling these lines down keeps them from floating high during the brief period between power-up and initialization. To use the pull-up/pull-down feature, you must first install 10 kilohm resistor packs in any or all of the four locations around the 8255, labeled PA, PB, PCL, and PCH. PA (RN3) and PB (RN6) take a 10-pin pack, and PCL (RN4) and PCH (RN5) take 6-pin packs. Figure 1-11 shows these locations. After the resistor packs are installed, you must connect them into the circuit as pull-ups or pull-downs. Locate the three-hole pads on the board near the resistor packs. They are labeled G (for ground) on one end and V (for Vcc) on the other end. The middle hole is common. PA is for Port A, PB for Port B, PCL is for Port C Lower, and PCH is for Port C Upper. Figure 1-11 shows a blowup of the pull-up/pull-down pads. To operate as pull-ups, solder a jumper wire between the common pin (middle pin of the three) and the V pin. For pull-downs, solder a jumper wire between the common pin (middle pin) and the G pin. For example, Figure 1-12 shows Port A lines with pull-ups, Port C Lower with pull-downs, and Port C Upper with no resistors. P6 U11 C11 RN6 PB G PB V V PA G PA RN3 74LS245 82C55 U10 74LS245 C10 SWITCH PCL U13 C13 S2 V G PCH PCH RN5 PCL V G RN4 TR5 TR6 TR7 TR8 S1 BASE ADDRESS TR1 TR2 TR3 TR4 5V 5V X1 X2 VEN IEN VOUT IOUT 5V 5V X1 X2 VEN IEN VOUT IOUT XTAL Y1 C7 U19 SWITCH RN1 RN9 P10 P9 AOUT4 AOUT3 C30 C29 C24 RN10 RN7 U20 C18 AOUT2 AOUT1 P7 P8 RN8 U21 82C54 C39 C37 C23 AD7237 AD7237 U17 U19 C41 C35 C36 C25 C42 AD694 U16 U23 C26 AD694 C34 C31 C15 AD712 C16 AD712 C40 C38 C32 C33 C17 AD694 C27 AD694 C28 P2 C19 C5 U5 OSC EC0 OT0 OSC EC1 74LS125 P5 74HCT08 CLK0 CLK1 C6 U15 U6 RN2 PAL 74LS244 P6 U11 C11 74HCT245 PB G PB U18 V V 82C55 PA PA RN3 U22 G 74HCT245 U10 C10 SWITCH OT1 OSC EC2 CLK2 U12 RN15 R1 P4 PCL U13 C13 S2 V G PCH PCH RN5 C14 Made in USA C21 U14 PAL C2 74HCT688 U2 R OT0 OT1 OT2 EXT PC3 PC0 RN4 V C3 G 74HCT243 74HCT138 U9 U3 74HCT367 P3 IRQ G U4 Real Time Devices, Inc. State College, PA PCL C9 C4 S3 C1 SWITCH U1 74HCT245 DA800 U8 74HCT243 + C20 C8 C43 C22,,,, Accessing the Analog World Fig Pull-up/Pull-down Resistor Circuitry 1-10

23 +5 V PA 8255 PULL-UP V G 10K PORT A (PA0-7) +5 V CL PULL-DOWN V G 10K PORT C LOWER (PC0-3) +5 V CH V G PORT C UPPER (PC4-7) Fig Adding Pull-ups and Pull-downs to Some Digital I/O Lines 1-11

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25 CHAPTER 2 BOARD INSTALLATION The DA800 board is easy to install in your IBM PC/XT/AT or compatible computer. This chapter tells you step-by-step how to install and connect the board for voltage outputs and 4-20 ma current loop outputs. After you have installed the board and made all of your connections, you can turn your system on and run the 800DIAG board diagnostics program included on your example software disk to verify that your board is working. 2-1

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27 Board Installation Keep the board in its antistatic bag until you are ready to install it in your computer. When removing it from the bag, hold the board at the edges and do not touch the components or connectors. Before installing the board in your computer, check the jumper settings. Chapter 1 reviews the factory settings and how to change them. If you need to change any settings, refer to the appropriate instructions in Chapter 1. Note that incompatible jumper settings can result in unpredictable board operation and erratic response. Also note that the P2 I/O connector mounting bracket has an oversized cutout to allow space for running the cable to 20-pin on-board connector P6 through the same I/O slot. If you want to run both cables through the same slot, you must make these connections before installing the board. To install the board: 1. Turn OFF the power to your computer. 2. Remove the top cover of the computer housing (refer to your owner s manual if you do not already know how to do this). 3. Select any unused short or full-size expansion slot and remove the slot bracket. 4. Touch the metal housing of the computer to discharge any static buildup and then remove the board from its antistatic bag. 5. Holding the board by its edges, orient it so that its card edge (bus) connector lines up with the expansion slot connector in the bottom of the selected expansion slot. 6. After carefully positioning the board in the expansion slot so that the card edge connector is resting on the computer s bus connector, gently and evenly press down on the board until it is secured in the slot. NOTE: Do not force the board into the slot. If the board does not slide into place, remove it and try again. Wiggling the board or exerting too much pressure can result in damage to the board or to the computer. 7. After the board is installed, secure the slot bracket back into place and put the cover back on your computer. The board is now ready to be connected via the external I/O connector at the rear panel of your computer. 2-3

28 External I/O Connections Figure 2-1 shows the DA800 s P2 I/O connector pinout and P6 on-board I/O connector pinout. Refer to these diagrams as you make your I/O connections. AOUT1 AOUT2 AOUT3 AOUT4 ANALOG GND ANALOG GND ANALOG GND ANALOG GND EXT INT EXT GATE ANALOG GND ANALOG GND ANALOG GND ANALOG GND ANALOG GND ANALOG GND ANALOG GND ANALOG GND DIGITAL GND DIGITAL GND PB0 PB1 PB2 PB3 PB4 PB5 PB6 PB7 +12 VOLTS -12 VOLTS PC0 PC1 PC2 PC3 PC4 PC5 PC6 PC7 +5 VOLTS DIGITAL GND DIGITAL GND PA7 PA6 PA DIGITAL GND PC7 PC6 PC5 P6 20-pin on-board I/O connector PA PC4 PA PC3 PA PC2 PA PC1 PA PC0 EXT CLK T/C OUT 0 EXT GATE T/C OUT 1 EXT CLK T/C OUT 2 EXT CLK VOLTS -12 VOLTS EXT GATE 2 +5 VOLTS DIGITAL GND P2 50-pin I/O connector Fig. 2-1 P2 and P6 I/O Connector Pin Assignments Connecting the Analog Outputs Voltage Outputs When the analog output is configured as a voltage output, the high side of the device receiving the output is connected to an AOUT line and the low side is connected to the corresponding ANALOG GND. Figure 2-2 shows how to connect the DA800 voltage outputs to a load. Connecting the Analog Outputs 4-20 ma Current Loop Outputs When the analog output is configured as a 4-20 ma current loop source, you can operate the loop using only the +12 volts supplied to the DA800 to power the current loop transmitters, or you can use external power supplies for dual power supply operation. Current Loop Operation, No Loop Power Supply: Figure 2-3 shows how to connect the current loop transmitter outputs to a resistive load with no external loop supply. The AD694 current loop transmitters used on the DA800 are designed to be stable when driving resistive loads. For inductive or poorly defined loads, it is recommended that you add a 0.01 µf capacitor in the location provided on the board for each analog output channel. The table included in Figure 2-3 lists each channel and its corresponding capacitor number on the board. These capacitors are located with the analog output circuitry on the top half of the board. The capacitor is placed between the output of the AD694 and analog ground, as shown in the circled area of Figure

29 OP- AMP BUFFERS 800 I/ O CONNECTOR P2 AD712 PIN 1 AOUT 1 LOAD PIN 2 ANALOG GND AD712 PIN 7 AOUT 4 LOAD PIN 8 ANALOG GND Fig. 2-2 Voltage Output Connections CURRENT LOOP TRANSMITTERS 800 I/ O CONNECTOR P2 AD694 PIN 1 AOUT1 AD694 PIN 1 AOUT 1 C24.01 µf LOAD PIN 2 ANALOG GND Channel Capacitor AOUT1 C24 AOUT2 C26 AD694 PIN 7 AOUT 4 AOUT3 AOUT4 C28 C30 LOAD PIN 8 ANALOG GND Fig. 2-3 Current Output Connections, No Loop Supply 2-5

30 Current Loop Operation, Single Loop Power Supply: Figure 2-4 shows how to connect the current loop transmitter outputs to corresponding loads with a single external loop supply not exceeding 24 volts. The AD694 current loop transmitters used on the DA800 are powered through the board by +12 volts. When operated with a +12 volt supply, the AD694 can source a current to a point as low as 24 volts below common. WARNING!! Be sure to observe the correct polarity when connecting the external loop supply. The positive terminal is connected to ANALOG GND, and the negative terminal is connected to the load side, as shown in the diagram! Failure to properly connect the supply can damage the board. Current Loop Operation, Multiple Loop Power Supplies: Figure 2-5 shows how to connect the current loop transmitter outputs to corresponding loads with an external loop supply not exceeding 24 volts in each loop. WARNING!! Be sure to observe the correct polarity when connecting the external loop supplies. The positive terminal is connected to ANALOG GND, and the negative terminal is connected to the load side, as shown in the diagram! Failure to properly connect the supply can damage the board. Connecting the Timer/Counters and Digital I/O For all of the digital connections, the high side of an external signal source or destination device is connected to the appropriate signal pin on the P2 or P6 I/O connector, and the low side is connected to any DIGITAL GND. Running the 800DIAG Diagnostics Program Now that your board is ready to use, you will want to try it out. An easy-to-use, menu-driven diagnostics program, 800DIAG, is included with your example software to help you verify your board s operation. You can also use this program to make sure that your current base address setting does not contend with another device. 2-6

31 CURRENT LOOP TRANSMITTERS 800 I/ O CONNECTOR P2 AD694 PIN 1 AOUT 1 LOAD PIN 2 AD694 PIN 7 AOUT 4 LOAD PIN 8 ANALOG GND + LOOP SUPPLY 24V MAX - Fig. 2-4 Current Output Connections, Single Loop Supply CURRENT LOOP TRANSMITTERS 800 I/ O CONNECTOR P2 AD694 PIN 1 AOUT 1 LOAD PIN 2 ANALOG GND + LOOP - SUPPLY 24V MAX AD694 PIN 7 AOUT 4 LOAD PIN 8 ANALOG GND + SUPPLY LOOP 24V MAX - Fig. 2-5 Current Output Connections, Multiple Loop Supplies 2-7

32 2-8

33 CHAPTER 3 HARDWARE DESCRIPTION This chapter describes the features of the DA800. The three major circuits are the D/A, the timer/counters, and the digital I/O. This chapter also describes the hardware-selectable interrupts. 3-1

34 3-2

35 The DA800 provides four analog output channels with voltage or 4-20 ma current loop outputs, three 16-bit timer/counters, and 24 TTL/CMOS digital I/O lines, as shown Figure 3-1. This chapter describes the hardware which makes up the major circuits and hardware-selectable interrupts. ADDRESS ADDRESS DECODE 12-BIT D/A CONVERTER V/I SELECT V/I SELECT AOUT1 AOUT2 12-BIT D/A CONVERTER V/I SELECT V/I SELECT AOUT3 AOUT4 INTERRUPT SELECT PC BUS PPI 24 BUFFERS AND PULL-UP/DOWN RESISTORS 8 ON BOARD CONNECTOR 8 16 I/O CONNECTOR DATA PIT 8MHz OSC TIMER/ COUNTER I/O SELECT 9 EXTINT CONTROL ±12 VOLTS +5 VOLTS Fig. 3-1 DA800 Block Diagram D/A Conversion The DA800 board performs digital-to-analog conversions on four independent analog output channels. The output of each conversion channel is jumper-selectable for ±5, ±10, 0 to +5, or 0 to +10 volts, or as a 4-20 ma current loop source. The AD bit D/A converter contains two independent D/A converter channels in a single CMOS package. The data to be converted is double buffered at the D/A input, which allows simultaneous updating of all eight D/A output channels. For voltage outputs, the AD712 precision operational amplifier provides complete coverage of the output voltage ranges. The exceptionally low offset voltage and drift ensure an accurate analog output on each channel. For current loop outputs, the AD694 current loop transmitter converts the voltage output of the D/A converter to a corresponding current between 4 and 20 ma. Digital I/O, 8255 Programmable Peripheral Interface The 8255 programmable peripheral interface (PPI) can be easily configured to solve a wide range of digital real-world problems. This high-performance TTL/CMOS compatible chip has 24 parallel programmable digital I/O lines divided into two groups of 12 lines each: Group A Port A (8 lines) and Port C Upper (4 lines); Group B Port B (8 lines) and Port C Lower (4 lines). 3-3

36 Each group can be programmed for one of three modes of operation. When operating in Mode 1, the on-board buffers must be removed from the Port C lines. When operating in Mode 2, both Port A and Port C buffering must be removed. This procedure is described in Chapter 1 in the S2 and S3 DIP switch discussion. The three operating modes are: Mode 0 Basic input/output. Lets you use simple input and output operation for a port. Data is written to or read from the specified port. Mode 1 Strobed input/output. Lets you transfer I/O data from Port A in conjunction with strobes or handshaking signals. Mode 2 Strobed bidirectional input/output. Lets you communicate bidirectionally with an external device through Port A. Handshaking is similar to Mode 1. These modes are detailed in the 8255 Data Sheet, reprinted from Intel in Appendix C. The bidirectional buffers on the 8255 s I/O lines monitor the 8255 control word to automatically set their direction. Hardware changes to the buffer circuitry are required only when using Mode 1 or Mode 2, where the Port A and/or Port C buffers must be removed as described in Chapter 1. Timer/Counters An 8254 programmable interval timer provides three 16-bit, 8 MHz timer/counters to support a wide range of timing and counting functions. These timer/counters can be cascaded or used individually for many applications. Each timer/counter has two inputs, CLK in and GATE in, and one output, timer/counter OUT. The clock sources for the timer/counters can be selected using jumpers on header connector P5 (see Chapter 1). The timer/ counters can be programmed as binary or BCD down counters by writing the appropriate data to the command word, as described in Chapter 4. The command word also lets you set up the mode of operation. The six programmable modes are: Mode 0 Event Counter (Interrupt on Terminal Count) Mode 1 Hardware-Retriggerable One-Shot Mode 2 Rate Generator Mode 3 Square Wave Mode Mode 4 Software-Triggered Strobe Mode 5 Hardware Triggered Strobe (Retriggerable) These modes are detailed in the 8254 Data Sheet, reprinted from Intel in Appendix C. Interrupts The DA800 can use any one of six signal sources to generate interrupts. These sources are: OT0, OT1, and OT2, which are the three 8254 timer/counter outputs; PC3, which is the INTRA signal from the 8255 PPI; PC0, which is the INTRB signal from the 8255 PPI; and EXT, an external interrupt you can route onto the board through the P2 I/O connector. Chapter 1 tells you how to set the jumpers on interrupt header connectors P3 and P4, and Chapter 4 provides some programming information. 3-4

37 CHAPTER 4 BOARD OPERATION AND PROGRAMMING This chapter shows you how to program and use your DA800 board. It provides a complete description of the I/O map and programming operations to aid you in programming. The example programs included on the disk in your board package are listed at the end of this chapter. These programs, written in Turbo C, Turbo Pascal, and BASIC, include source code to simplify your applications programming. 4-1

38 4-2

39 Defining the I/O Map The I/O map for the DA800 is shown in Table 4-1 below. As shown, the board occupies 20 consecutive I/O port locations. The base address (designated as BA) can be selected using DIP switch S1 as described in Chapter 1, Board Settings. This switch can be accessed without removing the board from the connector. The following sections describe the register contents of each address used in the I/O map. Table 4-1: DA800 I/O Map Register Description Read Function Write Function Address * (Decimal) 8255 PPI Port A Read Port A digital input lines Program Port A digital output lines BA PPI Port B Read Port B digital input lines Program Port B digital output lines BA PPI Port C Read Port C digital input lines Program Port C digital output lines BA PPI Control Word Reserved Program PPI configuration BA + 3 D/A Converter 1 LSB Reserved Program DAC1 LSB BA + 4 D/A Converter 1 MSB Reserved Program DAC1 MSB BA + 5 D/A Converter 2 LSB Reserved Program DAC2 LSB BA + 6 D/A Converter 2 MSB Reserved Program DAC2 MSB BA + 7 D/A Converter 3 LSB Reserved Program DAC3 LSB BA + 8 D/A Converter 3 MSB Reserved Program DAC3 MSB BA + 9 D/A Converter 4 LSB Reserved Program DAC4 LSB BA + 10 D/A Converter 4 MSB Reserved Program DAC4 MSB BA + 11 Updates the outputs of all Update All DACs Reserved DACs BA + 12 Reserved Reserved Reserved BA + 13 Enable and disable interrupt IRQ Enable Reserved generation BA + 14 Interrupt Status/Clear Read status of interrupt Clear interrupt BA Timer/Counter 0 Read TC0 count value Load TC0 count register BA Timer/Counter 1 Read TC1 count value Load TC1 count register BA Timer/Counter 2 Read TC2 count value Load TC2 count register BA Control Word Reserved Program control register BA + 19 * BA = Base Address 4-3

40 BA + 0: PPI Port A Digital I/O (Read/Write) Transfers the 8-bit Port A digital input and digital output data between the board and an external device. A read transfers data from the external device, through P2, and into PPI Port A; a write transfers the written data from Port A through P2 to an external device. BA + 1: PPI Port B Digital I/O (Read/Write) Transfers the 8-bit Port B digital input and digital output data between the board and an external device. A read transfers data from the external device, through on-board I/O connector P6, and into PPI Port B; a write transfers the written data from Port B through P6 to an external device. BA + 2: PPI Port C Digital I/O (Read/Write) Transfers the two 4-bit Port C digital input and digital output data groups (Port C Upper and Port C Lower) between the board and an external device. A read transfers data from the external device, through P2 and on-board I/O connector P6, and into PPI Port C; a write transfers the written data from Port C through P2 and P6 to an external device. BA + 3: 8255 PPI Control Word (Write Only) When bit 7 of this word is set to 1, a write programs the PPI configuration. The table at the top of the next page shows the control words for the 16 possible Mode 0 Port I/O combinations. D7 D6 D5 D4 D3 D2 D1 D0 Mode Set Flag 1 = active Mode Select 00 = mode 0 01 = mode 1 1x = mode 2 Group A Port A 0 = output 1 = input Port C Upper 0 = output 1 = input Mode Select 0 = mode 0 1 = mode 1 Port B 0 = output 1 = input Port C Lower 0 = output 1 = input Group B 4-4

41 8255 Port I/O Flow Direction and Control Words, Mode 0 Group A Group B Control Word Port A Port C Upper Port B Port C Lower Binary Decimal Hex Output Output Output Output Output Output Output Input Output Output Input Output Output Output Input Input Output Input Output Output Output Input Output Input Output Input Input Output A Output Input Input Input B Input Output Output Output Input Output Output Input Input Output Input Output Input Output Input Input Input Input Output Output Input Input Output Input Input Input Input Output A Input Input Input Input B When bit 7 of this word is set to 0, a write can be used to individually program the Port C lines. D7 D6 D5 D4 D3 D2 D1 D0 Set/Reset Function Bit 0 = active Bit Select 000 = PC0 001 = PC1 010 = PC2 011 = PC3 100 = PC4 101 = PC5 110 = PC6 111 = PC7 Bit Set/Reset 0 = set bit to 0 1 = set bit to 1 4-5

42 For example, if you want to set Port C bit 0 to 1, you would set up the control word so that bit 7 is 0; bits 1, 2, and 3 are 0 (this selects PC0); and bit 0 is 1 (this sets PC0 to 1). The control word is set up like this: Sets PC0 to 1: (written to BA +3) 0 X X X D7 D6 D5 D4 D3 D2 D1 D0 Set/Reset Function Bit X = don t care Bit Select 000 = PC0 Set PC0 BA + 4: D/A Converter 1 LSB (Write Only) Programs the DAC1 LSB (eight bits). BA + 5: D/A Converter 1 MSB (Write Only) Programs the DAC1 MSB (four bits) into D0 through D3; D4 through D7 are irrelevant. BA + 6: D/A Converter 2 LSB (Write Only) Programs the DAC2 LSB (eight bits). BA + 7: D/A Converter 2 MSB (Write Only) Programs the DAC2 MSB (four bits) into D0 through D3; D4 through D7 are irrelevant. BA + 8: D/A Converter 3 LSB (Write Only) Programs the DAC3 LSB (eight bits). BA + 9: D/A Converter 3 MSB (Write Only) Programs the DAC3 MSB (four bits) into D0 through D3; D4 through D7 are irrelevant. BA + 10: D/A Converter 4 LSB (Write Only) Programs the DAC4 LSB (eight bits). BA + 11: D/A Converter 4 MSB (Write Only) Programs the DAC4 MSB (four bits) into D0 through D3; D4 through D7 are irrelevant. DAC LSB D7 D6 D5 D4 D3 D2 D1 D0 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 DAC MSB D7 D6 D5 D4 D3 D2 D1 D0 X X X X Bit 11 Bit 10 Bit 9 Bit 8 BA + 12: Update DAC Outputs (Write Only) A write simultaneously starts a D/A conversion in all eight channels (data written is irrelevant). If the data has not been updated since the last conversion, the output of the DAC will not change. BA + 13: Reserved 4-6

43 BA + 14: IRQ Enable (Write Only) Enables and disables interrupt generation. Writing a 1 enables interrupt generation; writing a 0 disables interrupt generation. D7 D6 D5 D4 D3 D2 D1 D Interrupt Enable/Disable 0 = interrupt disabled 1 = interrupt enabled BA + 15: Interrupt Status/Clear (Read/Write) A read shows the status of the interrupt (bit 0 only) as defined below. A write clears the interrupt (data written is irrelevant). Each time the interrupt status bit goes high, a write should follow to clear the bit. D7 D6 D5 D4 D3 D2 D1 D0 X X X X X X X Interrupt Status 0 = no interrupt 1 = interrupt has occurred BA + 16: 8254 Timer/Counter 0 (Read/Write) A read shows the count in the counter, and a write loads the counter with a new value. Counting begins as soon as the count is loaded. BA + 17: 8254 Timer/Counter 1 (Read/Write) A read shows the count in the counter, and a write loads the counter with a new value. Counting begins as soon as the count is loaded. BA + 18: 8254 Timer/Counter 2 (Read/Write) A read shows the count in the counter, and a write loads the counter with a new value. Counting begins as soon as the count is loaded. BA + 19: 8254 Control Word (Write Only) Accesses the 8254 control register to directly control the three timer/counters. D7 D6 D5 D4 D3 D2 D1 D0 Counter Select 00 = Counter 0 01 = Counter 1 10 = Counter 2 11 = read back setting Read/Load 00 = latching operation 01 = read/load LSB only 10 = read/load MSB only 11 = read/load LSB, then MSB BCD/Binary 0 = binary 1 = BCD Counter Mode Select 000 = Mode 0, event count 001 = Mode 1, programmable 1-shot 010 = Mode 2, rate generator 011 = Mode 3, square wave rate generator 100 = Mode 4, software-triggered strobe 101 = Mode 5, hardware-triggered strobe 4-7

44 Programming the DA800 This section gives you some general information about programming and the DA800 board, and then walks you through the major DA800 programming functions. These descriptions will help you as you use the example programs included with the board. All of the program descriptions in this section use decimal values unless otherwise specified. The DA800 is programmed by writing to and reading from the correct I/O port locations on the board. These I/O ports were defined in the previous section. Most high-level languages such as BASIC, Pascal, C, and C++, and of course assembly language, make it very easy to read/write these ports. The table below shows you how to read from and write to I/O ports using some popular programming languages. In addition to being able to read/write the I/O ports on the DA800, you must be able to perform a variety of operations that you might not normally use in your programming. The table below shows you some of the operators discussed in this section, with an example of how each is used with Pascal, C, and BASIC. Note that the modulus operator is used to retrieve the least significant byte (LSB) of a two-byte word, and the integer division operator is used to retrieve the most significant byte (MSB). Many compilers have functions that can read/write either 8 or 16 bits from/to an I/O port. For example, Turbo Pascal uses Port for 8-bit port operations and PortW for 16 bits, Turbo C uses inportb for an 8-bit read of a port and inport for a 16-bit read. Be sure to use only 8-bit operations with the DA800! 4-8

45 Clearing and Setting Bits in a Port When you clear or set one or more bits in a port, you must be careful that you do not change the status of the other bits. You can preserve the status of all bits you do not wish to change by proper use of the AND and OR binary operators. Using AND and OR, single or multiple bits can be easily cleared in one operation. To clear a single bit in a port, AND the current value of the port with the value b, where b = bit. Example: Clear bit 5 in a port. Read in the current value of the port, AND it with 223 (223 = ), and then write the resulting value to the port. In BASIC, this is programmed as: V = INP(PortAddress) V = V AND 223 OUT PortAddress, V To set a single bit in a port, OR the current value of the port with the value b, where b = 2 bit. Example: Set bit 3 in a port. Read in the current value of the port, OR it with 8 (8 = 2 3 ), and then write the resulting value to the port. In Pascal, this is programmed as: V := Port[PortAddress]; V := V OR 8; Port[PortAddress] := V; Setting or clearing more than one bit at a time is accomplished just as easily. To clear multiple bits in a port, AND the current value of the port with the value b, where b = (the sum of the values of the bits to be cleared). Note that the bits do not have to be consecutive. Example: Clear bits 2,4, and 6 in a port. Read in the current value of the port, AND it with 171 (171 = ), and then write the resulting value to the port. In C, this is programmed as: v = inportb(port_address); v = v & 171; outportb(port_address, v); To set multiple bits in a port, OR the current value of the port with the value b, where b = the sum of the individual bits to be set. Note that the bits to be set do not have to be consecutive. Example: Set bits 3, 5, and 7 in a port. Read in the current value of the port, OR it with 168 (168 = ), and then write the resulting value back to the port. In assembly language, this is programmed as: mov dx, PortAddress in al, dx or al, 168 out dx, al Often, assigning a range of bits is a mixture of setting and clearing operations. You can set or clear each bit individually or use a faster method of first clearing all the bits in the range then setting only those bits that must be set using the method shown above for setting multiple bits in a port. The following example shows how this twostep operation is done. Example: Assign bits 3, 4, and 5 in a port to 101 (bits 3 and 5 set, bit 4 cleared). First, read in the port and clear bits 3, 4, and 5 by ANDing them with 199. Then set bits 3 and 5 by ORing them with 40, and finally write the resulting value back to the port. In C, this is programmed as: v = inportb(port_address); v = v & 199; v = v 40; outportb(port_address, v); 4-9