User`s guide

126 DC 900-1340I
BSC Programmer’s Guide
If the BSC 2780/3780 software receives a DLE EOT from the line, the client receives a
disconnect message with the
dlRead pOptArgs.usProtCommand field set to
DLI_PROT_SEND_DISC. If there were any outgoing queued messages, they are returned with
the
dlRead pOptArgs.usProtCommand field set to DLI_PROT_RESP_LOCAL_ACK, and the dlRead
pOptArgs.iICPStatus
field set to DLI_ICP_ERR_XMIT_ABORTED (transmission aborted by
EOT) error code.
The Send Disconnect command is also used during a signon sequence to reject an
invalid signon bid or response, as described in the next section.
An unsuccessful Send Disconnect command can return one of the following error codes
in the
dlRead pOptArgs.iICPStatus field (see Appendix D for error handling):
DLI_ICP_ERR_BAD_MODE
The function request is not available for the requested
access mode.
DLI_ICP_ERR_LINK_INACTIVE
The link is stopped.
5.4.1.10 BSC 2780/3780 Signon Command
Use the dlWrite function with the pOptArgs.usProtCommand field set to
DLI_PROT_SEND_SIGNON to send a BSC 2780/3780 Signon command. The pBuf parameter
points to a variable number of 8-bit bytes (up to 20) containing the signon ID.
The signon procedure consists of a bid–response sequence to exchange IDs between the
local and remote stations as a prelude to data transfer. Either station can initiate the
signon sequence. The BSC 2780/3780 software handles the signon line procedure, but
the client application is responsible for verification of remote and local IDs. The signon
procedure should be used only on the initial message; all subsequent messages are pre-
ceded by a normal line bid (ENQ without ID).
When the BSC 2780/3780 software receives a Signon command from the client, it places
the ID sequence before the ENQ character of the first line bid. The other station receives
the bid, verifies the ID sequence, and places its own ID sequence before the ACK0 of the