Teledyne 7600 - Infrared gas analyzer - communication manual - Manual (Page 10)

Teledyne Analytical Instruments
10
5.3 Response of slave station
(1) Response for normal command
To a relevant message, the slave station creates and sends back a response message which
corresponds to the command message. The composition of message in this case is the same
as in section 5.2. Contents of the data field depend on the function code. For details, refer to
Chapter 6.
(2) Response for abnormal command
If contents of a command message have an abnormality (for example, non-actual function
code is designated) other than transmission error, the slave station does not execute that
command but creates and sends back a response message at error detection.
The composition of response message at error detection is as shown in Fig. 5-2 The value
used for function code field is function code of command message plus 80H.
Table 5-1 gives error codes.
Station No.
Function code +80
n
Error code
Error check (CRC-16)
Fig. 5-2 Response message at error detection
Table 5-1 Error code
Error code Contents Description
01H Illegal function Non-actual function code is designated. Check
for the function code.
02H Illegal function A relative address of a resister number to which
the designated function code can not be used.
03H Illegal function Because the designation of number is too much,
the area where resister numbers do not exist is
designated.
(3) No Response
Under any of the following items, the slave station takes no action of the command message
and sends back no response.
A station number transmitted in the command message differs from the station number
specified to the slave station.
An error check code is not matched, or a transmission error (parity error, etc.) is detected.
The time interval between the composition data of the message becomes longer than the time
corresponding to 24 buts. (Refer to section 5.6: Transmission control procedure.)