9
Program
9.3. Error Detection Processing
In this program, the error detection processing is performed by means of dividing errors into
the following areas (1) to (3). For error codes, refer to 9.7. Error Processing.
(1)Errors when executing the CMND instruction (CMND instruction error)
Errors that occur at execution of the CMND instruction, such as the Unit error, command
format error, and parameter error, are detected as CMND instruction errors. An error is
detected with the related auxiliary area flag "Communications Port Error Flags (A219.07)"
when using the CMND instruction.
(2)Transmission errors when communicating with Destination Device (Communications error)
Errors occurred in communications with Destination Device, such as character corruption
and transmission errors caused by unmatched baud rate settings, are detected in CMND
instruction errors. Although the error is detected with (1), the allocated CIO area of SCU
''TransmissionErrorStatus (1508)'' is stored in the output area for the communication error
check.
(3)Errors in Destination Device (Destination Device errors)
Destination Device errors include a function code error, a register address error, a data error,
and an execution failure in Destination Device. An error is detected with the response data
which is returned from Destination Device. If an error occurs in Destination Device, a
function code that is obtained by adding #80 to the transmitted function code is returned. (in
this program, #83 is returned when #03 is sent.) This program detects an error based on the
difference between the send and receive function codes.
Send message
Register address
CRC16
Receive message
(at error)
**
CRC16
For information on the CIO area allocated to SCU, refer to 9.4.2 Lists of Fixed Allocations.
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