Siemens SIMATIC S5 CP 523 Manual page 154

CP 523
Message frames exceeding 256 bytes (5C
The peripheral device has sent a message frame that is longer than 256 bytes.
The CP flags error 5C
characters.
The message frame is not transferred to the CPU and not stored in the Receive mailbox.
Permanent wire break in the peripheral device cable (5D
During the transmission, the peripheral device must
• hold the RXD line constantly at logic "1" or
• hold the CTS line constantly at "ON" when using MODEM control signals ("ON": V 3 V).
Otherwise an error is flagged.
After a permanent break has been remedied, the sender can resume transmission when the
receiver has returned "XON". Data arriving at the receiver before the XON may be lost.
Receive mailbox overflow (5E
The following can be stored in the Receive mailbox:
• Up to 1024 bytes of data
• Up to 99 message frames.
If these values are exceeded when receiving a message frame from the peripheral device, the CP
flags an error.
The message frame is not transferred to the CPU and not stored in the Receive mailbox.
EWA 4NEB 811 6044-02a
)
H
if it has not detected an end-of-text character after receiving 256
H
)
H
Communications Mode
)
H
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