Intel MD566X - Manual (Page 34)

56K V.92 Data, Fax, and Voice Chipset
34 Intel Confidential Programmer’s Guide
The allowable connection modulations and data rates are determined by the +MS=m command,
which uses four parameters: , , , and .
The +MS=m parameter defines the top modulation rate.
The parameter determines whether the modem connection is allowed to fall down to
a lower modulation rate if the connection can not be made at a specified modulation or if the
modem connection can only take place at the specified modulation. Setting to 1
allows the modem to connect at a slower type than that specified. Setting to
0 allows the connection to use only the specified type.
The parameter defines the lowest data rate at which a modem connection can take
place. Setting to 0 has one of two meanings depending on the setting.
When both and are set to 0, then the lowest data rate at which the
connection can take place is the lowest data rate specified by the parameter. If
is set to 1 and is set to 0, then the lowest data rate is 300 bps.
The parameter defines the highest data rate at which a modem connection can take
place. If the is set to 0, the modem uses the DTE data rate or a slower data
rate as the highest permitted connection data rate. This highest-permitted data rate means the
modem attempts to connect at this data rate but may connect at a slower rate because of line
impairment. If and are set to 0 and the DTE data rate is below the lowest
data rate supported by the modulation rate, then the modem’s connection attempts always fail, and
the modem reports a “NO CARRIER” message.
If the +MS=m parameters contain conflicting information like “+MS=V34,1,14400,0” with a DTE
data rate of 2400 bps, then the modem’s connection attempts always fail, and the modem reports a
“NO CARRIER” message. This happens for two reasons. First, when the modem receives the
+MS=m command, the modem does not check for conflicts of valid parameter information.
Secondly, some of the same configuration information is provided by two other commands: Nn and
S37. The command issued last takes precedence.
The Nn command specifies whether the modem should attempt to establish a connection using a
single modulation type or allow the connection to fall to a lower modulation type. Nn performs the
same function as the +MS=m parameter. Whatever command is issued last
configures the modem for any following connections. Thus, upon receiving the +MS=m command,
the modem changes the value for Nn.
When configured to N0, the modem only attempts a connection at the rate specified by
S37, +MS=m, and Bn. If the remote modem does not support any of the data rates, the
modem does not achieve a connection and responds back with a “NO CARRIER” message.
When configured to N1, the modem attempts to connect to the remote modem at the highest speed,
as defined by S37, +MS=m, and Bn. Since not all modems support (or are configured for) the same
modem-to-modem data rates, the modems may connect at a lower speed.
+MS = , , ,
same as
Nn
same as
S37