Net-2000™ Voice Codec Unit
User’s Manual
Page 53
Section 3 – Net-2000™ VCU Control
DVSI Confidential Proprietary
Nack Packet Bytes 4 & 5 (seq)
Bytes 4 and 5 hold the 16-bit sequence number (see Table 5). The sequence number is used as a
method to detect if and when data packets are dropped, so it is important to ensure that consecutive
sequence numbers are transmitted for channel data packets during operation.
Seq
=
Sequence number*
Byte 4
7 6 5 4 3 2 1 0
Byte 5
7 6 5 4 3 2 1 0
Decimal
Value
Minimum Value
1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
-32768
Maximum Value
0 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
32767
Table 52 seq header parameter
*Note:
Sequence numbers should be incremented by one every time a packet is
transmitted. When the sequence number reaches 32767, the next valid sequence
number is -32768.
Nack Packet Bytes 6 & 7 (cmd)
The
cmd
element is used to indicate the packet type being Nack’ed.
Cmd parameter
Packet Type Nack’ed
Byte 6
7 6 5 4 3 2 1 0
Byte 7
7 6 5 4 3 2 1 0
Hex Value
Type
x x x x x x x x
x x x x x x x x
0xXXXX
Table 53 cmd parameter
Nack Packet Bytes 8 & 9 (reason)
The
reason
element is used to indicate the reason for the Nack. This value is currently always
0xFFFF (invalid packet). Other values are reserved for future expansion.
Cmd parameter
Packet Type Nack’ed
Byte 8
7 6 5 4 3 2 1 0
Byte 9
7 6 5 4 3 2 1 0
Hex Value
Packet Invalid
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
0xFFFF
Table 54 reason parameter