Brooks Instrument 0254 - Manual (Page 88)

C-10
Model 0254
Section C Serial Communications Protocol Installation and Operation Manual
X-SE-0254-eng
Part Number: 541B129AAG
September, 2010
C-4-1-6 Serial Message Error Control
Commands provide for error control of information packets sent by the
instrument. This is particularly useful when transferring information over
wide area networks, and causes the instrument to continue to send the
next packet or to resend a previous sent packet.
The send-resend is determined by the receiving host based on having
computed a checksum from the received characters, then comparing it
with the checksum sent by the unit. The instrument must be pre-configured
to enable the error control protocol.
Positive Acknowledge Command
This command must be issued by the receiving host to enable the
instrument to send its packet, which is next eligible. Should the instrument
not receive positive acknowledgement within four seconds, it will resend
the previous packet up to four times before abandoning the send session.
HOST SEND
AZA Non-network
AZ[yyyyy]A Network
RESPONSE - none
Negative Acknowledge Command
This command may be issued from the terminal or host to cause the
instrument to resend its previous packet. Should the instrument not receive
negative acknowledgement prior to a lapse of four seconds, it will
automatically resend the previous unacknowledged packet up to four times
before abandoning the send session.
HOST SEND
AZN Non-network
AZ[yyyyy]N Network
RESPONSE - none