User`s guide

102 DC 900-1340I
BSC Programmer’s Guide
4.22 3270 Text Addressing Option (27)
This BSC 3270 option determines whether IBM 3270 embedded addressing is per-
formed on inbound and outbound messages. The IBM 3274 cluster controller inserts
the address for the control unit (CU) and device in the first two bytes following STX of
the first block of a data or status message as follows:
If this option is set to disable, embedded address insertion and deletion is not per-
formed.
If this option is set to normal, a link configured as a tributary (3274 cluster controller)
automatically inserts the CU and device addresses into the first block of outbound mes-
sages. The addresses are derived from the CU and device number bytes in the
dlWrite
pOptArgs.usProtCircuitID
field. A link configured as a control station (3705 communica-
tions controller) extracts the embedded addresses from inbound messages. These
addresses are used to determine the CU and device number associated with the inbound
message.
If this option is set to automatic printer emulation, 3270 command checking is per-
formed, device status is kept, and printer emulation is performed. When a link using
this setting receives a valid 3270 write, erase/write, or erase/write alternate command
3270 Data Message 3270 Status Message
STX SOH
CU address %
Device address R
Te x t STX
ETX or ETB CU address
BCC Device address
Status bytes
ETX
BCC