Texas Instruments 990 User Manual page 238

Communications Structures
*
*
Any packets awaiting transmission are re-submitted for
packet level processing
A retransmission attempt is initiated Retransmission
attempts should be counted and a maximum of 3 to 5
retries is recommended for most types of secondary
stations. If the attempts still fail, then the
transmitting device must decide how to handle the
packets still in the queue for transmission.
The reset procedure causes queued packets to be renumbered.
Packets that are, unacknowledged when a reset request packet is
transmitted will remain unacknowledged thus raising the
possibility of duplicate packet transmission. It is recommended
that applications programs should be programmed accordingly and
duplication of data be considered preferable to deletion.
The format of the reset request packet is as follows:
BIT NUMBER
o
2 3 4 5 6 7
VIRTUAL
BYTE 0 0 0 0
1 CHANNEL
GROUP
LOGICAL CHANNEL NUMBER
2
0 0 0
1 1 0 1 1
3
0 0 0 0
0
0 0 0
4
DIAGNOSTIC CODE
2280621
where:
Byte 0 is the general format identifier, 0001, followed by
the virtual channel group (VCG) number.
Byte 1 is the logical channel number (LCN). VCG and LCN
together form the logical channel identifier (LeI).
Byte 2 is the reset packet type identifier.
Byte 3 is always set to zero.
Byte 4 is the .diagnostic code that points to the type of
problem encountered.
D-4
2270526-9701