Intel MD566X manual +MS = carrier , automode, min rate, max rate, S37

56K V.92 Data, Fax, and Voice Chipset

The allowable connection modulations and data rates are determined by the +MS=m command, which uses four parameters: <carrier>, <automode>, <min rate>, and <max rate>.

The +MS=m <carrier> parameter defines the top modulation rate.

The <automode> 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 <automode> to 1 allows the modem to connect at a slower <carrier> type than that specified. Setting <automode> to 0 allows the connection to use only the specified <carrier> type.

The <min rate> parameter defines the lowest data rate at which a modem connection can take place. Setting <min rate> to 0 has one of two meanings depending on the <automode> setting. When both <automode> and <min rate> are set to 0, then the lowest data rate at which the connection can take place is the lowest data rate specified by the <carrier> parameter. If <automode> is set to 1 and <min rate> is set to 0, then the lowest data rate is 300 bps.

The <max rate> parameter defines the highest data rate at which a modem connection can take place. If the <max rate> is set to 0, the modem uses the DTE data rate or a slower <carrier> 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 <max rate> and <automode> 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.

+MS = <carrier >, <automode>, <min rate>, <max rate>

same as	same as
Nn	S37

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 <automode> 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 <carrier> rate specified by S37, +MS=m, and Bn. If the remote modem does not support any of the <carrier> 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.

34 Intel Confidential Programmer’s Guide