IBM 5251 Series Maintenance Information Manual page 175

Bit 7
o
=
Display station not busy
1
=
Display station busy
Bit 8
o =
No line parity error found
1
=
Line parity error found
Bit 10
Indicates there is feature data to be sent or status
data from an I/O device to the controller.
Bits 11, 12, and 13
These three bits are encoded to indicate the
following exception status:
Bit 11 12 13
o o o
o o
o
o
o o
o
o
Bit 14
Description
No exception
status
Null or attribute
error
Activate command
not valid
Command or device
ID not valid
Input queue or
storage overrun
Register value
not valid
Power-on transition
By analyzing bit 14, the controller can determine
if the information in the received response
frame is the same as the information in the
preceding response frame, or if the information
has changed. Bit 14 is set to zero (0) after
power on. Any change in the response frame
changes bit 14 from its preceding condition.
Theory 5251 MIM 4-15