PCB Piezotronics 441A35 - Appendix A: Rs-232 Control

443B101/443B102 7
Manual 19854 Rev. D
ECN 50523
Appendix A: RS-232 Control
For RS-232 communication, the port settings should be as follows:
General
RS-232, DCE interface, XON/XOFF flow control,
Asynchronous protocol
Baud Rate
9600 Baud
Start Bits
1
Data Bits
8
Parity
None
Stop Bits
1
The message format is as follows:
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.
Command
Contains the command followed by any associated data. See below for command
structure, and command set for examples.
End Byte
ETX (0x03) - marks the end of the message.
Data Checksum
16 bits - the ASCII hex of the 8-bit sum, ignoring overflows, of all bytes in the message
including SOT and ETX bytes.
All messages sent to the rack will receive a response. A typical command transaction is shown below.
Host Rack
Command
ACK [data]
NACK [reason]
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.
The Format of an ACK Message
Start
Byte
(0x02)
Destination
ID
(Rack/Slot)
Command
End
Byte
((0x03)
Checksum
Start
Byte
(0x02)
ACK
(0x06)
Data
Field
End
Byte
(0x03)
Checksum