AM3270/TR3271 Reference Manual

Bisync Procedures
Bisync Protocols—Concepts and Terminology
086705 Tandem Computers Incorporated 1–13
Figure 1-4 shows the basic message sequences in polling and selecting.
Figure 1-4. Poll and Select Message Sequences
005
Supervisory Station
Tributary Station
(Polled/Selected
Terminal)
Time
(i) Ready-to-receive
(ii) Busy, Status Pending
(Poll Address) ENQ
SOH/Header/STX/
Text/ETX BCC
ACK0
EOT (Address)
(i) Data-to-send
(Poll Address) ENQ
EOT
(ii) Nothing-to-send
Select
Poll
(Select Address) ENQ
ACK 0
STX/TEXT/ETX/BCC
(Address) EOT
ACK 1
(Select Address) ENQ
RVI
WACK
Transparent Mode While AM3270 and TR3271 do not support line-level transparency, a general
description of this concept might be helpful, and so is included here. Note, however,
that they do support transparency for subdevices.
On occasion a message is sent that contains reserved control characters, such as when
sending a binary or program file. The character-recognition function can be
temporarily turned off, so that any accidental bit sequences in the message block data