Appendix A: Rs-232 Control - PCB Piezotronics 441A35 Installation And Operating Manual

Appendix A: RS-232 Control

For RS-232 communication, the port settings should be as follows:
The message format is as follows:
Start Byte
(0x02)
Start Byte STX (0x02) - marks the start of a new message.
Destination ID 16 bits - rack code (0-3 ASCII) followed by slot address (0-9 ASCII). Messages meant
for the master will have "MM" in this field.
Contains the command followed by any associated data. See below for command
Command
structure, and command set for examples.
End Byte ETX (0x03) - marks the end of the message.
16 bits - the ASCII hex of the 8-bit sum, ignoring overflows, of all bytes in the message
Data Checksum
including SOT and ETX bytes.
All messages sent to the rack will receive a response. A typical command transaction is shown below.
Command
The ACK/NAK field conveys information concerning the delivery of messages. The results of command
operations are contained in the data field of an ACK message. NAK reason bytes are defined below.
Start Byte (0x02)
Manual 23528 Rev. A
ECN 50523
RS-232, DCE interface, XON/XOFF flow control,
General
Asynchronous protocol
Baud Rate 9600 Baud
Start Bits 1
Data Bits 8
Parity None
Stop Bits 1
Destination ID
(Rack/Slot)
Host
ACK (0x06)
The format of an ACK message.
Command End Byte
((0x03)
Rack
ACK [data]
NACK [reason]
Data Field End Byte (0x03) Checksum
441A152 PEAK METER
Checksum
8