8
Instrument
Identification
(01 to 99)
Parameter
Mnemonic
(Section 8.6)
BCC
(optional)
Reply
ACK
Sign
Data (up to 12 characters)
…8
COMMUNICATION
8.3
Reply Format – Figs 8.4 to 8.6
The C300 Controller replies to the command
using the reply format shown in Figs. 8.4 to
8.6.
8.3.1
Term
Clarification for Reply Format
Instrument Identification
– two characters
identifying the C200 Controller, 01 to 99.
Data
– usually up to six characters (including
decimal point) showing the new parameter
value.
However, up to 12 characters may be used if
identifying the Alarm Relay Assignment, i.e.
when using mnemonics Q1, Q2.
Error Code
– two-character mnemonic – see
Section 8.5.
Reply
– one ASCII control character (see
Appendix A1):
‘ACK’
– command understood
‘NAK’
– command not understood
‘ETB’
– end of multiple read reply
block.
Block Check Character (BCC)
– one character,
the arithmetic sum of the complete message
(excluding parity bits), transmitted by the
controller for error detection – see Appendix
A3 on page 28.
Fig. 8.4 Reply Format (Command Understood)
Instrument
Identification
(01 to 99)
Parameter
Mnemonic
(Section 8.6)
BCC
(optional)
Reply
Sign
Data (up to 12 characters)
ACK
ETB
ETB
Note
. This reply format may be repeated several times – see Example c) overleaf
The last reply line is always:
First reply
Replies
2 to n
Last reply
(n+1)
ETB
Fig. 8.5 Multiple Read Reply Format
Instrument
Identification
(01 to 99)
Error Code
BCC
(optional)
Reply
NAK
Fig. 8.6 Reply Format (Command Not Understood)
