
USING THE BDLC PROTOCOL
UNILINK HOST
ADAPTER B–14
USER MANUAL
(1) The host computer issues a SNRM to initialize the adapter and the
adapter
responds with a UA.
(2) The host computer then sends an I-Frame. The sequence counts are
both
zero since the SNRM was issued previously
. The
adapter does not
have any information to return, so it responds with an RR that
acknowledges
the I-Frame.
(3) The host computer sends another I-Frame with the N(S) count
incremented. This time the adapter has information to return and
sends an I-Frame. This I-Frame acknowledges the host computer’s
frame
with the N(R) subfield.
(4) The host computer has no further information and polls the adapter
with an RR, which also acknowledges the adapter’s I-Frame. The
adapter
also has no information and responds with an RR.
(5) The host computer continues to poll the adapter and this time the
adapter
has information to return.
(6) The host computer determines that no further communications are
needed and
issues the DISC command. The adapter responds with the
UA
and begins a hardware
reset. The host computer will have to wait a
minimum of seven seconds before issuing any further BDLC frames.
This
allows enough time for the power
-up diagnostics to complete.
(7)
Once the
adapter
is disconnected or in the “disconnected mode”, it will
respond
to any command other than a SNRM with the DM response.