Packet Header; Table 9 Channel Packet Header; Table 10 Len Header Parameter; Table 11 Type Header Parameter - Digital Voice Systems Net-2000 User Manual

Net-2000™ Voice Codec Unit
User's Manual
PC source code is provided on the CD included with the VCU that implements the protocol and can
be used with the VCU in File Mode to encode and decode speech.

Packet Header

Each packet in the protocol starts with a six-byte header containing a 16-bit integer indicating the
overall length of the packet in bytes, a 16-bit integer indicating the type of the packet, and a 16-bit
sequence number. The six-byte packet header for all data packets is shown in Table 2. An "x" is
used in all the tables in this description to indicate that a bit can take a value of 0 or 1.
Packet Header
Bytes
(msb-lsb)
0 – 1
2 – 3
4 – 5

Table 9 Channel Packet Header

Bytes 0 and 1 hold the 16-bit length of the packet (see Table 10 len header parameter). Maximum
packet length is 514 bytes. Bytes 2 and 3 hold the 16-bit packet type (see Table 11 type ). Bytes 4
and 5 hold the 16-bit sequence number parameter (see Table 12 seq header parameter) The
sequence number of a response to a command packet is the command packet sequence number
plus one. The sequence number is used as a method to detect that no data packets are dropped, so
it is important to ensure that consecutive sequence numbers are transmitted for voice and channel
data packets during operation.
len = Length (in bytes) of total packet (including header)
Minimum Value
Maximum Value

Table 10 len header parameter

type = Packet type
Command Packets
Reset
Encode
Decode
Response Packets
ACK
NACK
Voice
Channel

Table 11 type Header Parameter

DVSI Confidential Proprietary
Bits
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
x x x x x x x x
Byte 0
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 0
Byte 2
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Byte 2
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Section 3 – Net-2000™ VCU Control
Bits
Parameter Name
7 6 5 4 3 2 1 0
x x x x x x x x
x x x x x x x x
x x x x x x x x
Byte 1 Decimal
7 6 5 4 3 2 1 0
0 0 0 0 0 1 1 0
0 0 0 0 0 0 0 0 514 bytes
Byte 3 Decimal
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 0
0 0 0 0 0 0 1 1
Byte 3 Decimal
7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1
0 0 0 0 0 0 1 0
0 0 0 0 0 0 1 1
len
type
seq
Value
6 bytes
Value
0
2
3
Value
0
1
2
3
Page 28