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Computer Gateway User Manual 5-3 5/96

5.3.1

5.3.1 Single-Link Bisynch Sequences

Most CG applications are expected to use single-link communications. Each single-link

transaction starts with the line-bid sequence and ends with release of the line. The CG

conflict timeout has been set to 0.75 second to reduce delays. If possible, the host

computer timeout should be set similarly (for CM60 applications, the DPS6 timeout is set at

one second). The CG is assigned primary priority for contention resolution.

Simplified example of single-block text transfer for single link:

Line Bid Sequence

SENDER ENQ

RECEIVER ACK0

Single Block Text Transfer

SENDER DLE STX "transparent text" DLE ETX BCC

RECEIVER ACK1

End Transmission

SENDER EOT

Example of multiblock text transfer for single link:

Line Bid Sequence

SENDER ENQ

RECEIVER ACK0

First Block Text Transfer

SENDER DLE STX "transparent text" DLE ETB BCC

RECEIVER ACK1

Intermediate Blocks Text Transfer

SENDER DLE STX "transparent text" DLE ETB BCC

RECEIVER ACK*

Last Block Text Transfer

SENDER DLE STX "transparent text" DLE ETX BCC

RECEIVER ACK*

End Transmission

SENDER EOT

NOTES: 1) ACK* means the correct ACK0 or ACK1, which alternate.

2) NAK received in place of ACK* requires retransmission of that block.

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Computer Expressions 40CG Manual do Utilizador Página 175