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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 80
Table 5-1 gives error codes.
Error code
01H
Illegal function
02H
Illegal data address
03H
Illegal data value
(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.
・ A 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 bits. (Refer to section 5.6 Transmission control procedure)
10
Station No.
Function code + 80
Error code
Error check（CRC-16）
Fig. 5-2 Response message at error detection
Table 5-1 Error code
Contents
.
H
H
Description
Non-actual function code is designated.
Check for the function code.
A relative address of a resister number to which the
designated function code can not be used.
Because the designation of number is too much, the
area where resister numbers do not exist is
designated.
INZ-TN5A1190-E
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