Experiment# 8: Photo-Interrupter Control

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Vernon O’Connor’
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1 Experiment# 8: Photo-Interrupter Control I. Objective 1. Study the schematic diagram of photo interrupter (PH1, and PH2) and the pulse generator circuit. 2. To demonstrate the control applications of photo-interrupter, for example controlling the direction of rotation of the step motor. II. Circuit Description The MTS-51 has two photo-interrupters PH1 and PH2. When light is blocked, the photo-transistor is cut-off and a low presents on the inverter output terminal. When light is not blocked, the photo-transistor conducts in saturation and a high presents on the inverter output terminal.

2 PH1 output can be connected to T1 or INT1 using a jumper cap on JP3. PH2 output can be connected to T0 using a jumper cap on JP4. The output signal of pulse generator is connected to pin 3 (OSC) of JP4. Using a jumper cap, the signal to T0 input of 8051 can be selected from PH2 output or pulse oscillator output. T0 (P3.4): Timer/counter 0 external input T1 (P3.5): Timer/counter 1 external input INT1 (P3.3): External Interrupt input 1 Exercise#1 Functional Description: Use PH2 output to control the direction of rotation of the step motor. When PH2 is not blocked by an object (for example a piece of paper), the step motor rotates CW. If PH2 is blocked by an object, the step motor rotates CCW. Connect Pins 1 and 2 together using a jumper cap. Source Program: Page 2 of 10

3 Program Description Exercise#2 Connect jp3 pins 2 to 3 and jp4 pins 1 to 2 1. Increment the value of counter every PH2 output pulse and decrement the value every PH1 output pulse, and show the result on DS3 and DS4. Page 3 of 10

4 Faculty of Engineering Biomedical Engineering Department Digital Logic Design and Computer Architecture Lab BME 438 Exp.8: Photo Interrupter Control Pre-lab Name: 10 Number: Page 4 of 10

5 1. According to exercise #1, complete the following Table according P3.4 Loop# P 2.0 P 2.1 P 2.2 P Write an assembly program that controls the rotation of the step motor as follows: a. Use PH1 output to control the direction of rotation of the step motor. When PH1 is not blocked by an object, the step motor rotates CW. If PH1 is blocked by an object, the step motor will rotate one revolution CCW and then rotate CW. b. Connect pin 2 and 3 of JP3 together using a jumper cap. Return to Exp# 5 for more information about interrupt registers and interrupt system control. Page 5 of 10

6 Experiment # 9: Output Port Expansion I. Objectives 1. Understand the serial components used in the MTS-51 trainer. 2. Demonstrates the technique of output port expansion using 8051 serial port in mode 0. II. Circuit Description The MTS-51 trainer contains three serial components 74164, 74165, and RS-232. DIP switch SW1 is used to select the serial components connected to RXD (P3.0) and TXD (P3.1) pins Figure #1 shows the circuit of output port expansion. This circuit is used to demonstrate the application of 8051 UART operating in mode 0. The data is serially transmitted from 8051 serial port to the input of serial -in parallel- out shift register The parallel outputs of are connected to BCD-to-7- segment decoder 74LS47 to drive 7-segment display, and connected to buffer 74LS240 to drive LEDs. Page 6 of 10

7 Exercise#1 Place SW1-1 and SW1-6 in ON position. Functional Description: 1. Sequentially turn on/off LEDs from left to right 4 times. 2. Sequentially turn on/off LEDs from right to left 4 times. Page 7 of 10

8 Source Program: ORG 000H MOV SCON,# B ;SET MODE 0 START: NR1: NL1: MOV R5,#4 ;SET COUNTER MOV A,# B RR A MOV SBUF,A ;SEND DATA JNB TI,$ CLR TI CALL DELAY JNB A.0,NR1 DJNZ R5,NR1 MOV R5,#4 ;SET COUNTER MOV A,# B RL A MOV SBUF,A ;SEND DATA JNB TI,$ CLR TI CALL DELAY JNB A.7,NL1 DJNZ R5,NL1 DELAY: MOV R6,#200 DL1: MOV DJNZ DJNZ RET END R7,#249 R7,$ R6,DL1 Page 8 of 10

9 Program Description Each byte of pattern data for LED control is sent through RXD to the serial in of SIPO shift register. To do so, three instructions are inserted into every instruction sequence for pattern data display. MOV SBUF, A ; used to transmit the pattern data through RXD JNB TI, $ ; checks to whether the 8-bit pattern data is transmitted or not. CLR TI ; clears transmit interrupt flag for next data transmission registers related to serial port: Registers SBUF and SCON are the most important registers in UART operation. 1. SBUF: Serial Data Buffer The SBUF is actually two separate registers, one transmits buffer register and one receive buffer register. When a byte data is moved to SBUF, it goes to the transmit buffer where it is held for serial transmission. When a byte data is moved from SBUF, it comes from the receive buffer. 2. SCON: Serial Port Control Register The serial port control and status register SCON locates in the address 98H of SFR. Its bit diagram is shown below. This register contains not only the mode selection bits, but also the 9 th data bit for transmit and receive (TB8 and RB8), and the serial port interrupt bits (TI and RI). Page 9 of 10

10 SM0 SM1 SM2 REN TB8 RB8 TI RI 1. SM0 (SCON.7): Serial port mode select bit 0 2. SM1 (SCON.6): Serial port mode select bit1 There are four modes in UART operation specified by the bits SM0 and SM1. A table of mode 0 is shown below. SM0 SM1 Mode Function Baud Rate Shift register Fosc/12 Mode 0 is usually used to expand the I/O lines. 3. TI (SCON.1): Transmit interrupt flag Set by hardware at the end of the 8 th bit time in mode 0, or at the beginning of the stop bit in the other modes, in any serial transmission. This flag must be cleared by software. 4. RI (SCON.0): Receive interrupt flag Set by hardware at the end of the 8 th bit time in mode 0, or halfway through the stop bit time in the other modes, in any serial reception (except see SM2). This flag must be cleared by software. Page 10 of 10

CoE3DJ4 Digital Systems Design. Chapter 5: Serial Port Operation

CoE3DJ4 Digital Systems Design Chapter 5: Serial Port Operation Serial port 8051 includes an on-chip serial port Hardware access to the port is through TXD and RXD (Port 3 bits 1 and 0) Serial port is