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CHAPTER 6 COMMUNICATIONS AMONG CPU MODULES
6
6.1 Communications Using the CPU Shared Memory
6.1.4 Communications among CPU modules when an error is detected
6.1.4 Communications among CPU modules when an error is
detected
This section describes the operations performed when an error is detected during data communications among CPU
modules using the CPU shared memory.
(1) Operation when improper data is received
If a CPU module receives improper data during data communications among CPU modules due to noise or
failure, the module discards the receive data. If the receive data is discarded, the CPU module holds the data
which was received before the discarded data.
When the module receives proper data next, the data will be updated.
(2) Data transmission when an error is detected
The operation status of auto refresh and data communications among CPU modules when the host CPU module
has detected a self-diagnostics error will be as follows.
: Transferred ×: Not transferred
*1 Auto refresh means data transfer between the internal user devices and the multiple CPU high-speed transmission area
in the host CPU module.
*2 Data communications among CPU modules means data communications between the multiple CPU high-speed
transmission area in the host CPU module and the multiple CPU high-speed transmission area in other CPU modules.
*3 If an error occurs during the normal operation, transmission of the normal data before the error is continued.
Even if data are written to the multiple CPU high-speed transmission area after the error, the data will not be sent to
other CPU modules.
*4 If a consistency check error occurs due to PLC parameter change during the normal operation, both auto refresh and
data communications among CPU modules are continued.
(3) Applicable CPU modules
The above operations are performed when any of the following CPU modules is used.
• Universal model QCPU (except the Q00UCPU, Q01UCPU, and Q02UCPU)
• Motion CPU (Q172DCPU(-S1), Q173DCPU(-S1), Q172DSCPU, or Q173DSCPU)
• C Controller module (Q12DCCPU-V, Q24DHCCPU-V, or Q24DHCCPU-LS)
Error definition
Auto refresh
*1
Data communications
among CPU modules
*2
Minor error
Moderate
error
Factors other than below
Multiple CPU high-speed transmission
function parameter error
(including the consistency check error)
×
*4
×
*3*4
Major error ×
×
*3