Siemens SIMATIC TIWAY 1 - Manual (Page 198)

USING THE BDLC PROTOCOL
UNILINK HOST ADAPTER B–13
USER MANUAL
B.6 ILLUSTRATIVE BDLC SEQUENCES
Example B–1 illustrates an error-free BDLC sequence between the host
computer and the adapter. This sequence shows how information is efficiently
transferred, since acknowledgements are part of the control subfield and does
not require a separate transmission.
Example B–1 BDLC Error-free Sequence
Host Computer
(1) SNRM
UA
(2) I–Frame, N(S)=0, N(R)=0, P
RR, N(R)=1, F
(3) I–Frame, N(S)=1, N(R)=0, P
I–Frame, N(S)=0, N(R)=2, F
(4) RR, N(R)=1, P
RR, N(R)=2, F
(5) RR, N(R)=1, P
I–Frame, N(S)=1, N(R)=2, F
(6) DISC
UA
... 7 second delay ...
(7) RR, N(R)=0, P
DM
UNILINK Host
Adapter