Texas Instruments 990 User Manual page 223

Throughput
B.7.4 Optional Data Field
The optional data field can be one of the following:
*
A control message, a three byte field. This is the same
as the first three bytes of the data packet shown below.
*
User data with control information. Details are shown
in the fo~lowing diagram:
Optional Data Packet Format
BIT NUMBER
o
2 3 4 5 6
BYTE 3
0 0 0 0
VCG
4 LOGICAL CHANNEL NUMBER (LCN)
5 P (R)
I
0
P
(s)
6 0 0 0 0 0 0 0
7 0 0 0 0 0
1 1
8
DID 010
9 DID 010
10
SOURCE 10 SOURCE 10
1 1
SOURCE 10
SOURCE 10
12
USER
MESSAGE
n-3
2280619
2270526-9701
B-ll
7
I
0
0
1
T
X.25 DATA
PACKET
HEADER
+
MESSAGE
TYPE
t
DESTINATION
AND
SOURCE IDs
+
USER DATAl
MESSAGE
~