COURIER HIGH SPEED MODEMS
In non-ARQ mode, a Courier set to &I5 operates as though flow control were disabled (&I0); it does not look for your typed XON/XOFF commands. However, it looks for XON/XOFF characters coming in over the phone link. When the remote operator sends XON/XOFF com- mands, the Courier either resumes or stops transmitting data over the link and drops the characters from the data stream.
If both modems are set to &I5, operators at each end can signal the remote modem to stop sending, thereby controlling the data flow on the phone link and preventing their own modem's buffer from overflowing. At the computer or terminal/modem interfaces, the modems independently control the flow of data through their Transmit Data (&H) settings.
Guidelines
Use of software flow control may prove satisfactory if you're only transferring text files. However, if you're transferring non- text (binary) files, or using an Xmodem-type protocol, disable flow control entirely (&R1, &I0). In addition, set the modem to &B0 and &N0, so that the serial port and connection rates are equal.
S-REGISTERS
The S-Registers are used to set various timing parameters, redefine selected ASCII characters, and other configuration options. A detailed summary of the S-register functions is in Appendix B. A less detailed summary is in the Quick-Reference card.
Sr=n Set S-Register value: r is any S-Register; n must be a decimal number between 0 and 255.
Sr.b=n Alternative command for setting bit-mapped registers: r is the bit-mapped register; .b is the bit; n is 0 (off) or 1 (on).
Sr? Query contents of register r.
Data Mode Operations 4-29
