User manual

Computer Gateway User Manual 4-13 5/96
4.2.2
4.2.2 Message Confirmation
This message is used to confirm that all blocks of a message have been properly received.
Each message except Time Synchronization or Link Failure (and the Message Confirmation
message itself) must be confirmed by the receiver (either host processor or CG) before the
next message can be sent by the originator. A negative confirmation requires the originator
to retransmit all blocks of the original message.
Header information: Word 1—Transaction Code = 30
Word 2—Number of Words = 1
Word 5—CG Identifier = 5
Word 8—Reason for Negative Confirmation
0=Block out of sequence
1=Illegal Transaction Code
2=Illegal CG Identifier
3=Number of words out of range
4=Number of blocks out of range
5=Block data too small
6=Block data size conflict
7=Block header conflict
8=Message size conflict
9=Message timeout
Message format: Word 1—Confirmation status (integer) 1=negative
2=positive
Use information: Note the use of header word 8 in a negative message confirmation
to indicate the CG's reason for rejecting the message. These error
reasons generally point to software problems at the host
processor.
For single-block messages, the Number of Blocks and Block
Number must both equal one.
For multi-block messages, the Block Number of each succeeding
block must increase sequentially from one to the Number of
Blocks value.
Any problems with format or content of Time Synchronization or
Message Confirmation messages as received by the CG (or
timeout on either) causes the CG to immediately stop link
communications and to issue a System Error Journal report.
With each negative Message Confirmation message, the CG also
issues a report to be included in the LCN System Error Journal.
See paragraph 5.7 for an illustration of these reports.