User`s guide

196 DC 900-1340I
BSC Programmer’s Guide
A.2.1 Normal Mode
A tributary link operates in normal mode when it acts as only one control unit. Normal
mode is in effect when the station ID option is set to a CU number from 0 to 31.
When the link is started, the BSC 3270 responds to only those poll and select sequences
that contain the configured control number. All other sequences are received but
ignored.
A.2.2 Test Mode
If the station ID option is set to 32, the tributary link enters “test mode.” While in this
configuration, the tributary link can respond as multiple control units on the same line.
The tributary link specifies the active control unit numbers with a Set Poll List com-
mand (Section 3.4.1.7 on page 62). In test mode, the tributary link responds to poll and
select sequences directed to any of the control units specified in the poll list and ignores
the rest.
A.3 Line Up/Down Reporting
If CTS and/or clock signals are missing, then BSC 3270 notifies the client with the
DLI_PROT_RESP_ERROR error report containing the DLI_ICP_ERR_XMIT_TIMEOUT error code.
At that time, all ICP message buffers that are queued for transmission are discarded.
The client receives the
DLI_PROT_RESP_LOCAL_ACK data acknowledge with the
DLI_ICP_ERR_XMIT_TIMEOUT error code for each discarded message buffer.
If the signal(s) return and line activity resumes, BSC 3270 sends the client the
DLI_PROT_RESP_ERROR error report containing the DLI_ICP_ERR_LINE_UP informational
code, and normal line operation is resumed.