USING THE BDLC PROTOCOL
The next example, Example B–2, illustrates errors in sequence counts, invalid
commands, and timeouts.
Example B–2 BDLC Error Sequences
Host Computer
(1) I–Frame, N(S)=1, N(R)=0, P
SNRM
I–Frame, N(S)=0, N(R)=0, P
(2) FRMR
(3) I–Frame, N(S)=3, N(R)=2, P
I–Frame, N(S)=3, N(R)=2, P
(1)
This sequence illustrates an error with the adapter's receive count. To
clear this condition, the host computer issues a SNRM to reset the
counts and it resets its internal counts, then retransmits the original
I-Frame.
(2)
This sequence illustrates an invalid command condition since the
FRMR is not a valid command to the adapter, to which it responds with a
FRMR.
(3)
This sequence illustrates a timeout. The host computer did not receive a
response from the adapter before the internal 30 ms time period
expired. The host computer then retransmits the I-Frame, which is
acknowledged by the adapter.
UNILINK Host
REJ, N(R)=2, F
RR, N(R)=1, F
... timeout ...
RR, N(R)=4, F
B–15
Adapter
UA
FRMR
UNILINK HOST ADAPTER
USER MANUAL