Hardware Information Communication Error "Sio" Occurs - Mitsubishi Electric MELSEC iQ-R Series User Manual

Hardware information communication error "SIO" occurs

Symptom
Hardware information
communication error "SIO"
occurs.
27 TROUBLESHOOTING
466
27.3 Troubleshooting by Symptom
Cause Corrective action
The stop bit settings do not
match.
Transmission speed is too
fast and the next data is
transmitted before C24
completes processing of the
receive data.
Data larger than the receive
buffer size was received.
■Remarks
For the nonprocedural protocol, data up to the end code
received at first or fixed length data is stored in the
nonprocedural reception buffer memory area, and C24 turns
ON the read request to the CPU module.
When the next data is sent while the read request is ON, the
data is temporarily stored in the operating system receive
buffer. When the operating system receive buffer becomes full,
C24 skips the rest of the data and turns ON the "SIO" LED.
During multidrop connection,
two or more devices
transmitted data at the same
time.
• Match the stop bit settings of C24 to that of the target
device.
• Decrease the transmission speed and restart data
communications.
• Use the DTR and DC controls to interrupt transmission
before the buffer becomes full.
Perform RS/CS control when the modem function is used.
• Lengthen the transmission interval and take sufficient time
for the read processing of the CPU module side.
• Connect the target devices to C24 on a 1:1 basis and
perform a communications test.
If C24 can communicate normally with each of all target
devices, two or more devices transmit data simultaneously
during multidrop communication. Therefore, interlock the
devices not to transmit at the same time.
MC Non Bi Pd
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