Dr. Dobb's Journal, June 1987 - Extended COM Port Driver
Buffered input - no lost data
input flow control - XON/XOFF or control lines
output flow control - control lines
works with existing software
removal - without reboot
19,200 and 38,400 baud operation
type ahead with CRT's
Excom is functionally equivalent to the BIOS int 14h COM port
handler with three significant enhancements:
1. it provides interrupt-driven buffered input
2. it has an extended set of configuration parameters
3. it has flow control selection and higher baud rates.
Excom is made up of three major sections, the COM port data
input interrupt handler, the replacement for the BIOS int14h handler,
and the code to install and initialize Excom.
Install EXCOM early in the boot process - BEFORE a PRINT/D
Using EXMODE to install
the book says use EXMODE to remove
1. Control-S (^S) and Control-Q (^Q) are sent without any regart
to the UART being ready or the control lines being correct.