Specifications

Net-2000™ VCU Users Manual
Version 4.0, December, 2013
(Subject to Change) Page 36
Interface Protocol
Digital Voice Systems, Inc.
The Speech Compression Specialists
6 Interface Protocol
The VCU implements a channel data interface using a special protocol designed by DVSI. The Net-2000™-VCU
VCU packet is described from the point-of view of the Net-2000™-VCU.
6.1 Serial Port Protocol
The RS-422 interface protocol is exactly the same as the Ethernet protocol interface but, with an extra 16-bit sync
word so that sync up can done in the middle of a transmission.
6.2 Ethernet Protocol
The Net-2000™-VCU uses port 4000 for communication of channel and voice data across the Ethernet interface.
Port 4000 -- the Net-2000™-VCU sends channel/voice data over this port when the channel/voice interface is
Ethernet. It also uses this port for vocoder commands. The default port number is 4000, but a different port number
can be assigned by using the web interface control and selecting the Net-2000™-VCU settings button.
Note: Port numbers 4001, 4002 and 4003 are reserved by the Net-2000™-VCU and
must not be used. Valid port numbers are greater than 1024 and less than 65535.
6.3 Packet Protocol Description
The Ethernet protocol of the Net-2000™-VCU’s uses port 4000. Byte order for all 16-bit data types (“short” in the
C-language data structure) is network order (big endian), so bytes with lower indexes are the most significant. Since
PC’s are little endian machines it is necessary to byte-swap when using this protocol with a PC.
The VCU utilizes two categories of packets: Command Packets and Response Packets. Command Packets are
received by a VCU from another VCU in VOIP mode or from a connected PC in File Mode. Command Packets
direct a VCU to perform a specific action such as decoding or encoding voice data or performing a reset operation.
Response Packets are generated by a VCU and are either the result of a vocoder operation, a reset operation or an
unrecognized received packet. Command and Response Packets have five different formats:
Channel Data Packets
Contains channel data output by the VCU encoder (coded speech) or input to the VCU decoder to synthesize speech.
Decode Command Packets and Channel Response Packets use the Channel Data Packet format.
Voice Data Packets
Contains 8kHz sample rate 16 bit PCM voice data that are inputs to the VCU encoder or are synthesized outputs of
the VCU decoder. Encode Command Packets and Voice Response Packets use the Voice Data Packet format.
Reset Packets
Reset Packets are used in File Mode to initialize the encoder and/or decoder.
Ack Packets
Ack Packets are used in File Mode to confirm that a Reset Packet was executed successfully.
Nack Packets
Nack Packets are transmitted by the VCU in response to an invalid received packet.
DV
SI CONFIDENTIAL PROPRIETARY