The Bus Command Sequence - Brainboxes PS-307 User Manual

Mode 7 Overview
For unambiguous data output to the IEEE bus devices use
the OUTPUT command.
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The BUS Command Sequence.

All data output from the controlling computer's RS232 port
is inspected for the following sequence of bytes:-
<Carriage Return> BUS
Here B is the Ascii character decimal 66.
U is the Ascii character decimal 85.
S is the Ascii character decimal 83.
<Carriage Return> is Ascii character decimal 13.
One or more Carriage Returns and Line Feeds, Ascii
character 10, may be inserted before the BUS
characters.
After receiving the <CR> BUS sequence the data following
up until a trailing <CR> with optional <LF> is treated as an
Ascii string containing IEEE bus keywords and numeric
parameters. These keywords are interpreted as commands to
perform Serial or Parallel Polls, send any IEEE bus commands
or specify the timeout period.
The command interpreter checks the syntax of your IEEE
string and responds with 'All done OK' or 'Error in command'
as appropriate.
If an error has been detected then all the commands in the
received string prior to the error will have been executed. The
exact place the error occurred is given by the field in the IEEE
control status string positioned at bytes 44-46. The value in this
field is the position of the byte in the previous BUS command
that the PSI BOX did not recognise, the PSI BOX starts
counting from the B in BUS as position 1.
In addition to the PSI BOX responding with the message
'Error In Command' there is a syntax error flag is the byte at
Chapter 7
PSI BOX Reference
Page 73