Siemens SIMATIC TIWAY 1 User Manual page 193

B.4 COMMANDS AND RESPONSES
The following subset of the ANSI X3.66 standard is supported by the UNILINK
Host Adapter:
D
D
D
D
D
UNILINK HOST ADAPTER
USER MANUAL
USING THE BDLC PROTOCOL
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".
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.
Power-up diagnostics requires a minimum of 7
seconds to complete. During this time the adapter
will not respond to any host communications.
UA — The Unnumbered Acknowledgment command is sent by the
adapter in response to the SNRM and DISC commands to acknowledge
their reception.
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".
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.
NOTE
B–8