Chapter 4 – Voice Commands
Multi-Tech Systems, Inc. AT Commands for the MultiModem & SocketModem MT9234 Series (S000434H)
56
+VPP
Enable or Disable Voice Mode Packet Protocol
Description:
The +VPP command enables and disables the Packet protocol for Voice mode
operation, and handles the new unsolicited Voice mode result codes. The Packet
protocol is used to detect lost octets on the modem-to-PC serial link, and to recover
the lost octets by requesting retransmission. The Packet protocol assumes that the
data corruption is not a problem on the communications link, the last octet sent will
never be lost due to data overrun (i.e., that the newer octets always overwrite
previous octets in the communications input buffer, a common UART design feature).
Several PC processes can cause serial input channel neglect for longer than the
Protocol time between asynchronous characters (typically less than 521
microseconds), and data loss can occur. If a character is lost in the received data,
the playback of the voice data may be impaired or lost. If a character is lost in the
final result code, the connection may fail. The Packet protocol permits recovery from
such data loss.
Syntax: AT+VPP=<enable>
Values:
0, 1; (2–255 reserved for future standards)
Result Codes:
OK if the modem accepts the command.
ERROR if the <enable> value is out of range.
+VPR
Select DTE/DCE Interface Rate (Turn Off Autobaud)
Description:
The +VPR command causes the modem to select between various fixed modem-to-
PC interface rates and autobauding. The selected fixed interface rate stays in effect
until the modem selects another interface rate or autobauding, or until the modem
returns to autobauding on the expiration of the Inactivity Timer. The newly selected
rate takes effect after the modem returns the OK result code.
Syntax: AT+VPR=<rate>
Values:
+VPR=0
select autobauding
+VPR=1
select 2400 bps
+VPR=2
select 4800 bps
+VPR=3
select 7200 bps
+VPR=4
select 9600 bps
+VPR=5
select
12000
bps
+VPR=6
select
14400
bps
+VPR=7
select
16800
bps
+VPR=8
select
19200
bps
If the modem claims support for autobauding (+VPR=0), it means that the modem
can accept AT commands at 2400 bps at all times while in Voice command mode
and with +VPR=0.
Result Codes:
OK if the modem accepts the command.
ERROR if the <rate> value is out of range.
electronic components distributor
