Digital Voice Systems Net-2000-P25, Руководство пользователя

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Net-2000™ Voice Codec Unit
User’s Manual
Page 35
DVSI Confidential Proprietary
Section 4 – Net-2000™ VCU Interface Protocol
Nack Packet Parameters
len
The len parameter (bytes 0 and 1) hold the 16-bit length of the packet (Table 3). The packet length
is ten bytes.
len = Length (in bytes) of total packet (including header)
Byte 0
7 6 5 4 3 2 1 0
Byte 1
7 6 5 4 3 2 1 0
Decimal
Value
Ack Packet Size 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 10 bytes
Table 32 len header parameter
type
The type parameter (bytes 2 and 3) is 16-bits packet type and is always 0x0001 for nack packets.
type = Packet type
Byte 2
7 6 5 4 3 2 1 0
Byte 3
7 6 5 4 3 2 1 0
Hex Value
Nack 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0x0001
Table 33 type header parameter
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 34 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.
cmd
The
cmd
element is used to indicate the packet type being Nack’ed.