SIOX-RS232C Converter

Transcription

1 L40 SIOX-RS232C Converter p 2 TELEFRANG AB TABLE OF CONTENTS SIOX-RS232C Converter General Description This module connects a CRT terminal or other RS232C serially communicating I/O device as a station on a SIOX 2-wire bus. Baud rate, bit format and handshaking can be defined in an internal EEPROM. Buffers in both transfer directions permit continuous, bidirectional transmission of both text, data and other asynchronous protocols. The 2-wire SIOX bus connection is optoisolated from the rest of the module. Block Diagram L40 Versions...1 Installation and Power Supply...3 Status Indicators...3 Start-Up...3 Communication Examples...4 Setup and RS232 Modes...5 Parameter Overview...6 Parameter Detailed Description...7 RS232 Serial Port Signals...12 Electrical Characteristics...13 Environmental Specifications...13 Mechanical Specifications...13 Versions : L40 SIOX to RS232 Converter H:\L40\Man\L40man.wpd/ /TC

2 L40 SIOX-RS232C Converter p 3 L40 SIOX-RS232C Converter p 4 Installation and Power Supply The L40 RS232 Converter is equipped with two connectors, one female 25- way D-sub connector for the RS232 device and one 4-way Phoenix MSTB for the SIOX bus. Either connector can be used for the power supply, 12 V to 35 V DC. Current consumption with unloaded outputs is approximately 12 ma. Short-circuiting of an output pin in the D-sub connector should be a- voided since it increases consumption and causes internal heat build-up. The polarity of the two SIOX bus leads is arbitrary, and they are opto-isolated from the rest of the L40 and the connected terminal. Status Indicators Two LED's on the L40 module indicate the SIOX bus status. The green LED is lit when loop voltage is applied. During transmission of a "zero" bit (from the master or any of the stations) this LED is off, and any communication on the bus causes it to flutter. When the green LED is constantly off, the SIOX bus is inoperable. The red LED is on only when the module transmits "zero" bits, thus indicating that the SIOX communication is active and the L40 module is answering. Start-Up When power and SIOX bus have been connected, the module is ready to run. Unless otherwise requested, the module is set up at the factory to communicate at 4800 bits/s using SIOX address 0/1. General principles for the SIOX bus and communications are described in a separate manual, the "SIOX System Description". Changes in operation modes and addressing are brought about by Parameter Setup Strings communicated over the SIOX bus, as described below. L40 contains a 512 bytes buffer for receiving characters from the RS232 device. At each communication initiated from the central computer, L40 transfers 1-80 characters from the buffer to the central. Note that L40 will not discard the characters from the buffer until it is confident that the central has received them properly. L40 therefore monitors next communication and frees the buffer unless that turns out to be a retransmission. Any characters received from the central are stored in another buffer of 384 bytes and output to the RS232 device as soon as possible. To be able to communicate, the device must be ready, i.e. the RTS (Request To Send) line pulled high. When not connected, L40 assumes that RTS is high. In case of any communication problems, always check that lines 2 and 3 measure a negative voltage and RTS and CTS a positive voltage with respect to GND. Communication Examples L40 can handle communications in an arbitrary mix of Data Mode (containing maximum one character to the RS232 device and one from the device), String Texts (max 80 characters in both directions), String Setup (read or write one parameter in RAM or EEPROM) and String Setup Enquiries (for info on module type or parameter explanations). These standardized message types are further described in the manual "SIOX System Description". Communication software for various types of central computers is available from Telefrang. Below follows some examples of how the messages are transferred over the SIOX bus. Hex codes are used to describe the characters. 1. Double Data Mode to station 9 from the central containing the IBM 8-bit character "ü" = hex 81: C9 0/1 0/1 Address 9 7 LSbits 8th bit Answer from L40: 0/0/ 7C bits 0/-6 bits 7-13 = hex 3E0/0/ = 0/0/ / 0/0/0/0/ 0/0/0/0/ (RTS and DTR high, no character) 2. String Mode text request from the central to station 9: C0/ 49 BE 78 Address 9 (Empty) Signoff/Checksum Answer from L40 containing "TEXT" received from the RS232 device: BE 7C T E X T Signoff/Checksum

3 L40 SIOX-RS232C Converter p 5 L40 SIOX-RS232C Converter p bytes String Mode transfer from central employing both repeated and meta (8-bit) characters: C0/ /5 B0/ 0/5 BE 3A Address 9 0/5 0/5 0/5 0/5 85 Signoff/Checksum Empty answer from L40: BE 41 Pos. Value Function hex hex Parameter Overview 0/0/ 8xxx Monitor, permits write to prohibited areas. 4xxx No Text Characters in String Answers. 4. String Mode Setup to RAM parameter #0/0/ = 0/70/1: C0/ 0/ / 30/ 37 30/ 31 BF 0/B Address 9 Write Par. 0/0/ Data = 0/70/1 Signoff/Chk Confirmation from L40: 30/ 37 30/ 31 BF 78 0/ 7 0/ 1 Signoff/Chk 2xxx 1xxx x9xx-x3xx No Text Characters in Data Mode Answers. 2 Data characters transmitted in Data Mode. SIOX Transmission Speed control bits/s. x0/xxx2xx or xaxx-xfxx = default 4800 bits/s. Setup and RS232 Modes The L40 contains two types of memory: RAM for temporary storage for as long as the module is connected to a power supply, and EEPROM for longterm storage of working modes when the power supply is disconnected. At power-up, the EEPROM is automatically copied to the RAM, and the information is used to control the module. Using String Mode commands, described in "SIOX - a Communication Method", any variable may be read or modified at any time, either temporarily in RAM or permanently in EEPROM. In the latter case, the corresponding RAM cells are modified as well. The MS-DOS program SIOXUSER permits quick access to these parameters if a PC compatible and a K30/K32 SIOX adapter are available. Alternately, the SIOX display module P10 permits the user to read and change the setup of another SIOX module. xx0/1 FFFF Only 1 SIOX Address accepted. The module is restarted by writing hex FFFF. 0/1 0/1xx-3Fxx Address nr xx1x xxx4 Compress multiple equal text characters in String Mode answers. Repeated X-ONs every 10 s if no activity. xxx2 Send Data Mode "empty" answer char = hex 80/. xxx1 Transfer NUL from central computer in Data Mode. 0/2-0/3 0/0/0/0/ Options reserved for specific customers. 0/4 0/1xx-50/xx Message Length maximum text length in a String Message to the central. 0/5 x0/xx-xfxx RS232 Mode set-up. xxx1-xxx9 RS232 Baud Rate set-up: or default /6 XXYY X-ON / X-OFF Characters for software handshaking, typically 1113 or 0/0/0/0/.

4 L40 SIOX-RS232C Converter p 7 L40 SIOX-RS232C Converter p 8 Pos. Value Function hex hex 0/7 8xxx Handshaking Status: Receive from RS232 possible 2xxx RTS Pin=ON Transmit to RS232 permitted 1xxx DTR Pin=ON (No effect on L40) x8xx CTS Pin=ON Receive from RS232 possible Parameter # 0/0/, Speed Select The SIOX bus transmission speed is changed by setting one of the following values: x9xx = bits/second x8xx = 9600 bits/second x7xx = 4800 bits/second x6xx = 2400 bits/second x5xx = 1200 bits/second x4xx = 600 bits/second x3xx = 300 bits/second x4xx Handshaking Status: Transmit to RS232 permitted Other values=default: 4800 bits/second xxxf Parameter Detailed Description Reset Command Flags causing a single operation Parameter # 0/0/, Monitor Control Flag It is possible to write to prohibited areas in RAM and EEPROM if this parameter is set at 8xxx. The Monitor Flag should in all normal cases be cleared. When writing to this and other multiple-function parameters, be careful to include the flags below, setting all 16 bits simultaneously. Parameter # 0/0/, String / Data Answer Inhibit If text is fetched alternately in String Mode and one character at a time in Data Mode, the central might get problems reorganizing the text again. Setting either of these flags 4xxx or 2xxx causes answers in String Text Mode or Data Mode, respectively, to be empty. In this way it is possible e.g. to send text in String Mode without expecting anything in return and poll L40 in Data Mode for single character answers. Parameter # 0/0/, Double Data Flag Depending on the communication protocol, 4 or 5 bytes Data Mode communication can be defined. 4 bytes (using 7 output data bits) are suitable for normal ASCII character transfers. 5 bytes (using 14 output data bits) can be selected by setting the parameter to 1xxx, permitting 8-bit characters to be transferred in Data Mode. String Mode is not affected by the Data Mode selected. The speed parameter, when changed from the central computer, must be set in EEPROM, and be followed by a power-down / power-up cycle, to have effect. Parameter # 0/0/, Number of Addresses In the same parameter, the number of communication addresses is defined for compatibility with other SIOX modules. Any number except xx0/1 is invalid and will immediately revert to 0/1 in the RAM copy of the EEPROM parameter. Restart of the module is accomplished by writing hex FFFF to parameter 0/0/. For example, to change the baud rate of a remote L40, first write the corresponding code into EEPROM parameter 0/0/, then write hex FFFF to the same parameter (in EEPROM or RAM). The module will now restart and commence communication on the new baud rate. Parameter # 0/1, Address The station address is defined by this parameter. 0/1xx-3Fxx are valid, while 41xx-7Fxx, 81xx-BFxx, C1xx-FFxx automatically reverts to 0/ 1xx-3Fxx. Note that an address change also affects later String Mode parameter set-up communications. Selecting address 3F for normal communication should be avoided, since this is a default address for uninitiated modules.

5 L40 SIOX-RS232C Converter p 9 L40 SIOX-RS232C Converter p 10 Parameter # 0/1, Feature Flags There are five flags included in this parameter. First, when the bit value xxx4 is set and X-ON is activated but no input is received from the RS232 device, a new X-ON is returned to the device every 10 seconds. Adding xxx2 to parameter # 0/1 permits compatibility with older SIOX modules using the eighth bit of the Data Mode answer as a "no data" flag. When all characters input from the RS232 device have been transmitted, the NUL code is used in the answer, but with xxx2 set, hex 80/ is used in a "no data" answer to distinguish it from a real NUL character. However, in RS232 8-bit mode, even 80/ is a valid character, so 0/0/ must be used when no character is available, irrespective of the parameter flag. Setting the parameter to xxx1 permits Data Mode "NUL" characters from the central computer to be buffered and sent to the RS232 device if this is necessary. Normally, when the parameter contains xxx0/, NULs are not buffered, since they are also used when the module is prompted for an answer character from the device without any character to send. The prompting NULs might otherwise overflow the buffer. In String Mode an empty string may be sent from the central computer when only an answer string is requested, so NULs found in the string are always buffered. To identify a real character in both 7- and 8-bit RS232 mode, the ninth bit of the answer is always set when a character is transmitted. Thus, when the parameter contains xxx0/, the 14-bit answer word will be 3E0/0/ when empty, 3F0/0/ for a NUL and 3FXX for other characters. Parameter # 0/4, Message Length The SIOX protocol defines the maximum string length as 80 characters. To guarantee a worst case poll time, L40's permitted string length can be reduced by setting this parameter to between hex 0/1xx and 50/xx. This defines the answer string length to between 1 and 80 characters. Other values are illegal and will revert to 80. Setup messages are not affected. This message length maximum also affects the sign-off character terminating an answer string. If the free space in the buffer from SIOX to RS232 is larger than the predefined message length, the sign-off characters BC - BF are used. Otherwise B8 - BB are used, signalling that the central computer should hold off any further strings. Meanwhile, empty strings can fetch more text from the RS232 device and query the L40 when the buffer will accept more. In other cases, there is a risk that, at next text message from the central, the buffer will still be full and L40 must refuse the message. This will lead to unnecessary retransmissions and delays. Parameter # 0/5, RS232 Mode/Baud Rate Format and speed for the RS232 device can be changed dynamically in RAM or EEPROM by setting/clearing the following bits: Adding 0/0/10/ to parameter # 0/1 permits L40 to compress String Mode answers when contiguous identical characters from the RS232 device have been received. The communication driver in the central computer must then be able to unpack such an answer. Parameters # 0/2-0/3, Options In normal use, these parameters should be set at 0/0/0/0/, since modes to customers' individual specifications may be activated by other values. 0//1/2 = 4800 b/s; 3 = 300 b/s; 4 = 600 b/s; 5 = 1200 b/s; 6 = 2400 b/s; 7 = 4800 b/s; 8 = 9600 b/s and 9 = b/s Examples: 1 At delivery the setup for the RS232 device is 0/60/8 = 7 data bits, even parity and 2 stop bits at 9600 bits/s. 2 0/80/7 = 8 data bits, no parity bit and 1 stop bit at 4800 bits/s. Parameter # 0/6, X-ON / X-OFF Characters

6 L40 SIOX-RS232C Converter p 11 L40 SIOX-RS232C Converter p 12 In software handshaking, a character is sent back to the transmitting device when transmission should be suspended or resumed. In L40, these characters are selectable in this parameter from the normal 0/0/0/0/ (no soft handshake at all) to e.g. X-ON = hex 11 (ASCII DC1) and X-OFF = hex 13 (ASCII DC3). When active, an X-OFF is sent to the RS232 device when less than 128 characters are free in the receiving buffer. If the device stops transmitting and characters are fetched by the central so that the free buffer increases to 384 characters, an X-ON will be sent. When the buffer is all empty, a new X- ON is sent every 10 seconds in case the first was lost. Similarly, when the RS232 device sends an X-OFF, L40 will halt transmission to the device and resume when an X-ON has been received. The handshake characters are excluded when messages are transferred to the central. Parameter # 0/7, Status & Reset Flags The first half of this parameter contains the same status bits that are included in a Data Mode answer. Please look below at "RS232 Serial Port Signals". The least significant four bits of parameter 7 are single operation flags which are automatically cleared after the operation. Flag xxx8 flushes the buffer from the RS232 device to avoid making several Data or String Text communications when the collected data is considered irrelevant. Flag xxx4 flushes, in a similar way, data already sent to L40 but not yet transferred to the RS232 device. Flag xxx2 causes one extra X-ON to be transferred to the device. Flag xxx1 causes one extra X-OFF to be transferred to the device. RS232 Serial Port Signals The 25-way female connector can be plugged into many types of terminals, personal computers or other types of RS232 devices. In some cases, the cable supplied with the terminal must be installed between the terminal and the adapter connector, or a special male-to-male gender changer, e.g. to a modem, must be used. Pin Name L40 to Terminal Levels etc. # Terminal to L40 1 Prot.Gnd Not connected in L40 2 Tx X -3 V V 3 Rx X -9 V; short-circuit 10 ma 4 RTS X +3/ V (int. pullup) 5 CTS X -9 V; short-circuit 10 ma 6 DSR X -9 V through 1 k 7 Signal Gnd 8 DCD X +9 V through 1 k 9 V+ X +12 V V supply 20 DTR X +3/ V (int. pullup) The CTS line is pulled low when the input buffer of L40 is filled with characters received via the Tx pin but is otherwise active = high. DSR and DCD outputs are always active = high. If the RTS line is driven low from the terminal device, the L40 will halt transmission of characters to the terminal. RTS and DTR input levels are reported back to the central computer in each Data Mode communication. When left unconnected, they are held active = high by internal pull-ups. Typical 14-bit Data Mode answer (when the protocol in the central has compacted the received bits). The first 8 bits can also be read in String Setup Mode as parameter 7:

7 L40 SIOX-RS232C Converter p 13 Electrical Characteristics Power Supply: Min Typ Max Unit Supply Voltage V Current, all I/O off 12 ma RS232 I/O Pin Loading: Inputs (at -12 V) -30 IA Outputs (at -9 V) - 1 ma (short circuit) -10 ma Environmental Specifications Operating Temp. Range *C Storage Temp. Range *C Mechanical Specifications Size 60 x 40 x 15 mm Weight 40 g