Siemens SIMATIC S5 CP 521 Manual page 181

ASCII Mode
Table 7-35. Status Byte in ASCII Mode (PII) (Continued)
Byte 0
Bit 4 to 7 Bit 0 to 3
1 X
2 X
3 X
4 X
5 X
6 X
8 X
X= Signal status for other byte half irrelevant
7-58
Clock defective
Default time set
Time/date error
Illegal job
Coordination information (only after job "Coordinate
data transfer")
Data transfer from the CP 521 to the CPU
Hardware error
Status
GWA 4NEB 812 6030-02b
CP 521