Siemens SIMATIC TIWAY 1 - Manual (Page 193)

USING THE BDLC PROTOCOL
UNILINK HOST ADAPTER B–8
USER MANUAL
B.4 COMMANDS AND RESPONSES
The following subset of the ANSI X3.66 standard is supported by the UNILINK
Host Adapter:
D SNRM — The Set Normal Response Mode command is issued by the
host computer to logically activate the adapter’s host interface and/or to
reset the send and receive sequence counts. A SNRM must be sent to the
adapter before any other command when the adapter is in the
“Disconnected Mode”.
D DISC — The Disconnect command is issued by the host computer to
logically deactivate the adapter’s host interface and forces the adapter
to perform a hardware reset which executes the power-up diagnostics.
When the adapter receives the DISC command, it will first respond with
a UA and then begin the reset. The adapter will not respond to any
commands until it has completed the power-up diagnostics.
NOTE
Power-up diagnostics requires a minimum of 7
seconds to complete. During this time the adapter
will not respond to any host communications.
D UA — The Unnumbered Acknowledgment command is sent by the
adapter in response to the SNRM and DISC commands to acknowledge
their reception.
D DM — The Disconnect Mode response is returned by the adapter any
time the host issues a command other than an SNRM when the adapter
is in the ”Disconnected Mode”.
D RR — The Receive Ready command is used by the host computer to poll
for data and by the adapter to indicate the reception of a message and/or
that the host can send another message.