Texas Instruments 990 User Manual page 241

Communications Structures
The format of the RNR 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 P (R)
I
0
0 1
0 1
2280623
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 (LCI).
Byte 2 is the RNR packet identifier.
0.3.4
Receive Ready Packet
A receive ready (RR) packet is sent under the following
conditions:
*
*
After an RNR packet is transmi tted and the transmi tting
station is again able to receive data packets, that is,
the RNR condition is cleared.
When a receive window is full, to acknowledge data
packets if no data packets are queued for transmission.
Refer to paragraph
0.4
for further information on
windows.
A receive
conditions:
ready packet is received under the following
*
After the reception of an RNR packet and the sending
station has cleared the RNR condition.
* To acknowledge receipt of a data packet.
2270526-9701 D-7