Ack Characters - Honeywell CIU 888 Protocol Manual

A- 6
Appendix A - GPU Communication Protocol
Spelled out in bits:
Char Parity
STX 0
1 0
R 0
X 0
8 0
8 0
8 0
0
R 0
1 0
0 1
0 1
ETX 1
BCC 0
A.6 ACK characters
The computer system always initiates communication with the CIU
using a command record. After sending this record, the computer
system must wait for a reply from the CIU in the form of an answer
record. After the turn around time, an answer record may be sent.
But if the CIU is still busy preparing its reply - or if it is otherwise
engaged in field communication - the CIU transmits ACK characters
about every 50 milliseconds. These characters are an acknowledgment
of the command record, and show that the CIU intends to send an
answer record to the computer system as soon as possible. The timeout
period of the computer system should start again on reception of an
ACK character from the CIU. When a command record is accepted and
being processed (i.e. ACK characters are sent every 50 milliseconds) a
new command is not accepted. The CIU 888 service tool and CIU 888
web interface provides an option to disable the ACK characters sent to
the host system, refer to the Configuration Manual CIU 888 (Part No.
4417584) for more information.
Protocol Manual - CIU Emulation
CIU 888
b6 b5 b4 b3 b2
0 0 0 0 0
0 1 1 0 0
1 0 1 0 0
1 0 1 1 0
0 1 1 1 0
0 1 1 1 0
0 1 1 1 1
0 1 0 0 0
1 0 1 0 0
0 1 1 0 0
0 1 1 0 0
0 1 1 0 0
0 0 0 0 0
1 0 0 0 0
b1 b0 Comment
1 0 Start of transmission
(excluded from BCC
calculation)
0 1 CIU address
1 0
0 0
0 0
0 0
0 0
0 0 Space
1 0
0 1
0 0
0 0
1 1 End of transmission
1 1 Calculated over 7 bits
Part No.: 4417589_Rev13