User`s guide

204 DC 900-1340I
BSC Programmer’s Guide
A.4.4 BSC 3270 Sense/Status Message
Status and sense conditions are recorded by the BSC 3274 control unit for each attached
device. These conditions include busy or ready status or detected errors. All remote sta-
tus and sense conditions are combined into two bytes (per device), which are always
sent in a status message from the 3274. In EBCDIC code, the sense/status bytes are sent
as printable EBCDIC characters. In ASCII code, they are translated to ASCII characters
before they are sent. Figure A–9 shows the sense/status bytes as they would appear in
Sun memory byte ordering. Figure A–10 shows the format of a status message as it is
transmitted on the communication line.
The ICP sends status messages to the BSC 3270 master based on changes in device sta-
tus or errors detected in the 3270 command stream. Although there are 256 possible
Figure A–9: BSC 3270 Sense/Status Bytes
Figure A–10: BSC 3270 Status Message Format
1CRIRECC
data check
equipment check
intervention required
command reject
device end (ready bit)
unit specify
device busy
DC R OC1RRDBC US DE R
S/S 1S/S 0
operation check
C – 0 or 1 to make byte appear as a printable EBCDIC character
1 – always a 1
R – reserved
%RSTXcuadaSOH s/s 0 s/s 1 ETX BCC
cua = control unit address
da = device address
s/s 0 = sense/status byte 0
s/s 1 = sense/status byte 1