User manual

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.