AM3270/TR3271 Reference Manual

What are Bisync Protocols?
Bisync Protocols—Concepts and Terminology
1–4 086705 Tandem Computers Incorporated
Figure 1-2. Basic Message Block
002
SYN SYN SOH
Control characters used to identify header, text, and trailer include:
SOH
Header
STX
ETX
BCC
= Start of Header. Transmitted before the header characters. Optional.
= Header Text. Optional.
= Start of Text. Transmitted before the first data characters.
= End of Text. Terminates a message block starting with SOH of STX.
= Block Check Character.
Legend
STX
Text
ETX BCCHeader
Data Flow
A multiblock message is one that contains multiple blocks of information. The first
block must contain a header, text, and a trailer. Subsequent blocks in the same
message may contain only the text and a trailer. The last block in the message contains
the ETX or ETB control character, as shown in Figure 1-3. Note that with a multiblock
message, SYN characters precede each block in the message.
Figure 1-3. Multiblock Message
004
Control characters used to identify header, text, and trailer include:
SOH
Header
STX
ETX
BCC
ITB
= Start of Header. Transmitted before the header characters. Optional.
= Header. Optional.
= Start of Text. Transmitted before the first data characters
= End of Text. Terminates a message block starting with SOH of STX
= Block Check Character
= End of Intermediate Transmission Block
Legend
SYN SYN SOH
Header
STX
Text
ITB BCC SYN SYN SYN SYN STX
Text
ETX BCC
Data Flow