INM MTL 130-0200 Rev 4138 COMMUNICATION PROTOCOLCommunication parameters are 9600 Baud, 8 bits, no parity, 1 stop bit and no handshaking. Theinstrument is DTE. The general form of the protocol is:1. The protocol is a single command and response protocol.2. A command consists of an “address” and an “action”. A received valid address isalways responded to even if the action is invalid. Commands must be single you cannotsend multiple commands without awaiting a response.3. A Response consists of a “tag” and “data”.4. A command message can not be more than 30 characters without message terminator(). Exceeding this length will result in an error 90. response5. A response message can not be more than 30 characters without message terminator(). Exceeding this length will be assumed to be a communications error.6. A command message timeout is defined as 10 seconds. This is the maximum timefrom a valid address “Ax” to the message terminator ().This time is long to allow keypad entry (i.e. HyperTerminal)7. The response message failure to respond timeout is defined as 300 milliseconds. Thisis the maximum time from a valid command message terminator (). Untilthe first character of the response.8. A response message line maximum duration is defined as 1 second. This is themaximum time from the first valid response character to the line message terminator().9. A response message maximum duration is defined as 3 second. This is the maximumtime from the first valid response character to the last message terminator(). This is to allow multiple line responses. No card response can hold thebus for more than 3 seconds. Factory commands are the only exception10. exceptions to 7,8,9• Starting up: The card start up is defined as taking up to 10 seconds. The cardwill then assert an error “97” in R1, R4 and R5 on the first reading after the 10second period. Subsequent readings will show the correct values.• Calibration exemption from paragraph 7 and 8 but must comply with paragraph 9.The general form of the response is:1. Read whole group: ‘AxP0’ where x is the network address of the unit. The unit willrespond when x is its own address or 0 (any unit responds to address 0), otherwise itwill not respond at all. If No Zero Param bit in sysflags is set, ‘AxP’ OR ‘AxP0’ to send all.2. Read specific group item: ‘AxPy’ where y is the line (or item) number3. Write specific group item: ‘AxPy=. The format and (where appropriate)precision of the new value is as it is displayed. With the ‘verbose’ flag cleared: Pyitemname=value unit4. With the ‘verbose’ flag set: Py =value5. A read command will return 0 when it has no value to report(e.g. A0E6 returns A0E6=0)6. A ‘do now’ write command (e.g. clear logs ‘E6’) will do nothing if set with a 0 asargument, will execute with a 1 as an argument and will ?93 any other argument.A ‘do now’ write command returns 0 for fail and 1 for success.E.g. A0E6=1 returns A0E6=1
