title Processor to turn off COM DTR ; ; This program turns off the DTR signal on the communications ; port of a Zenith Z100 micro. This makes the Z100 compatible ; with the Gandalf PACX communications switch. The execution ; of this program should be the FIRST thing in the AUTOEXEC.BAT ; file. It MUST be before the DATE & TIME calls. ; ; This program is necesary because the vanila ZDOS leaves ; the DTR signal on after a reset or boot. A preferable ; solution would be to fix ZDOS, but this works too. Note that ; in either case it is the user's terminal emulator's resposibility ; to insure that DTR is raised at the beginning of a session AND ; lowered at the end. ; ; Mitch Blank ; name OFF code segment byte public 'code' assume cs:code,ds:code,es:code,ss:code org 100h start: mov al,4 ; Turn off DTR & RTS out 0EFh,al int 20h code ends end start