COURIER HIGH SPEED MODEMS
Data Rates
The modem can be set to a fixed or variable serial port rate. A fixed rate sets the modem for the highest possible throughput and provides the best performance. A variable rate allows the modem to switch to match the more limited rate on the phone connection.
Your software must support fixed or variable serial port rates, and must be set to either of the two settings. NOTE: Your software may refer to these options with terms like locked serial port (fixed rate) or autobaud (variable rate).
Most communications programs support variable rates, but not all software supports fixed rates.
WARNING: To connect above 9600 bps, the serial port rate must be 19.2K, 38.4K, 57.6K, or 115.2K bps. If the local computer is limited to 9600 bps, V.32 terbo modems are limited to 9600 bps maximum, that is, V.32. Disable V.32 terbo modulation so that the modem does not switch its serial port rate up higher than 9600 bps. Do this by setting Register S34 to 3 (S34=3) and including that setting in the defaults you write to nonvolatile memory, as shown in Setting/Using Defaults earlier in this chapter.
&Bn Serial port rate variable or fixed.
&B0 | Variable rates. When the modem switches its connection |
| rate to connect with a modem operating at a different |
| rate, it also switches its serial port rate. The software or |
| terminal also switches serial port rates to match the |
| connection rate. |
&B1 | Fixed rate. Default. The modem always communicates |
| with the terminal or computer at the rate at which you |
| have set the terminal or software, regardless of the |
| connection rate. For the greatest throughput, set the |
| serial port to 115.2K, 57.6K, 38.4K bps for high speed |
| calls and to at least 9600 bps for |
| This setting is not affected by the &N setting. However, |
| the serial port rate must be equal to or higher than the &Nn |
| rate. |
Data Mode Operations
