Siemens SIMATIC S5 CP 523 Manual page 47

CP 523
4.2.2 Communications Mode
Operation may be interrupted for various reasons in Communications mode. The following table
lists the effects of faults.
Fault
CPU goes to
STOP
*
POWER OFF
(CPU)
Fault in CP -
peripheral
device
connection
or
POWER OFF
(peripheral
device)
* The data transfer between CPU and CP (Send or Receive) is aborted. The job must be restarted following transition
from STOP to RUN. This is of particular relevance for the S5-135U / 150U / 155U.
** Data cannot be corrupted in 3964(R) mode, as the message frames are transmitted in a protocol message frame
( 7.4).
Note:
If you operate the RS-232-C (V.24) interface without handshaking (Handshake OFF), the CP 523
cannot detect a break in the connection between the CP and the peripheral device.
EWA 4NEB 811 6044-02a
Table 4-5. Faults in Operation (Communications Mode)
Comment
Battery backup
available
not available
Data traffic continues between CP and peripheral
device. This can lead to overflow of the Receive
mailbox.
Send and receive message frame data is lost
Clock data is retained
Clock data is lost
Data is corrupted during transmission (in both
directions)
**
CP error message
• Character time-out
• Peripheral device not ready (after 20 s)
• Permanent line break
Bad message frames in Receive mailbox
Notes on Operation
Effect
**
4-5