Ampro Corporation 486E manual COM Port Table, Serial Handshake

Product Reference

Note

Some programs that emulate an ASCII terminal do not properly support the basic ASCII command functions shown in Table 2–14. Ampro provides a suitable PC terminal emulator program, TVTERM, on the Common Utilities diskette.

The keyboard and screen of the terminal become the system console after system boots. Programs used this way must use ROM BIOS video functions rather than direct screen addressing for their display I/O. Keyboard data from both the external serial device and the standard AT keyboard can be entered.

Note

DOS programs that write directly to video RAM do not display properly on a serial console device.

COM Port Table

When the system boots DOS initializes the serial ports to 9600 baud (typical). To preserve the selected console port parameters stored in SETUP, the ROM BIOS can be instructed to delete the selected console port from the internal COM port table, normally used by DOS to locate the serial ports. With the port deleted from the COM port table, DOS cannot change its parameters. If you use a serial console, be sure to select the option that deletes the console port from the COM port table.

Serial Handshake

The serial console device data format and the Little Board/486e CPU serial port data format must match for the devices to properly communicate. In addition, the hardware handshake behavior must be compatible. Normally, a serial port’s Data Set Ready (DSR) and Clear To Send (CTS) input handshake signals must be true (active) for the ROM BIOS to send data out. On the

Little Board/486e CPU, the hardware handshake can be enabled or disabled with SETUP. When hardware handshaking is enabled, be sure to connect the DSR and CTS signals to appropriate handshake signals on the external serial device’s interface connector. As an alternative, loop the Little Board/486e CPU’s serial output handshake signals to its input signals as follows:

!DTR (out) to DSR (in)

!RTS (out) to CTS (in)

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