Siemens SIMATIC S5 CP 523 Manual page 153

Communications Mode
Table 7-25. Status Byte (Byte 0) in Communications Mode after "Coordinate Data Transfer"
Byte 0
Bits 4 to 7 Bits 0 to 3
5 9
*
5 A
*
5 B
*
5 C
*
5 D
5 E
*
* Signal state irrelevant for the other half-byte
Character delay time exceeded (59
The interval between two characters exceeds the value set in parameter block 7.
The data received up until this point is transferred as message frame to the CPU.
This is advantageous when you want to receive message frames of varied lengths although a fixed
message frame size has been specified. This works when an I/O device sends variable-length data
message frames without specific end-of-text characters and when the message frames arrive at
long intervals (manual entry).
Parity error (5A )
H
The parity of received characters does not agree with the parity configured in parameter block 0.
The message frame is not transferred to the CPU and is not stored in the Receive mailbox.
Receive after XOFF or receive after DTR = OFF (5B
In the case of XON/XOFF protocol:
The CP 523 sends XOFF to the peripheral device if
• less than 20 bytes are free in the Receive mailbox
• the CP has received 99 message frames.
The CP 523 sends XON again only when more than 256 bytes are free in the Receive mailbox.
When using MODEM control signals:
The CP 523 sends DTR = OFF to the peripheral device if
• less than 20 bytes are free in the Receive mailbox
• the CP has received 99 message frames.
The CP 523 sends DTR = ON again only when more than 256 bytes are free in the Receive mailbox.
Error XB is flagged if the peripheral device has sent more characters than the CP can
H
accommodate in the Receive mailbox. The message frame is not transferred to the CPU and not
stored in the Receive mailbox.
7-48
Character delay time exceeded
Parity error
Receive after XOFF or after DTR = 0
Frame exceeds 256 bytes
Continuous break in line to I/O device
Receive mailbox overflow
)
H
Status
)
H
CP 523
EWA 4NEB 811 6044-02a