;SEROUT.ASM
;use bit 0 of the Parallel port (pin2) of the Portfolio=20
;as serial output port up to 19200 baud!!
;reads a char from the keyboard and sends it
;ESC ends the program.
;NOTE the output level is TTL, but most PC's handle this OK!
;assemble with A86.
;Gerard Rutten, Boekel, Netherlands, september 97.

;fullbit =3D 54 for 4800 bd, 109 for 2400, 24 for 9600, 11 for 9200

fullbit equ     54               =20
halfbit equ     fullbit / 2
portin  equ     8078h
portout equ     8078h

sendtst:
        mov     dx,portout              ;set the port
        mov     ax,0                    ;set bit0 to low
        out     dx,al                   ;do it

        mov     ah,09                   ;send string function
        mov     dx,welcome              ;refer to welcome string
        int     021h                    ;do it

send1:  mov     ah,07                   ;get a key from keyboard in al
        int     021h                    ;do it

        cmp     al,27                   ;is it esc?
        je      stop                    ;if yes then return to dos

send2:  mov     ah,02                   ;display char in dl
        mov     dl,al                   ;move from al to dl
        int     021h                    ;do it

        call    sendbyt                 ;send it serial too

        jmp     send1                   ;keep on going

stop:    ret                            ;end program and return to dos

sendbyt:
;first add start and stop bits to al into ax and then send all bits in =
ax
;to bit 0 of port defined in portout
        push    ax                      ;save ax
        push    cx                      ;save cx
        push    dx                      ;save dx

        mov     ah,3                    ;2 stop bits high
        shl     ax,1                    ;1 start bit low
        not     ax
        mov     dx,portout
        mov     cx,11                   ;11 bits to send
l1:
        out     dx,al
        shr     ax,1

        push    cx
        mov     cx, fullbit             ;wait a bittime
sendb2: loop    sendb2
        pop     cx

        loop    l1                      ;loop till cx =3D0
        pop     dx                      ;restore dx
        pop     cx                      ;restore cx
        pop     ax                      ;restore ax
        ret                             ;return

welcome:db      'Serial (c) G.w.Rutten',0a,0d,
        db      'Sends typed chars serial (4800 bps) via bit 0 of =
Portfolio PI',0a,0d
        db      'press ESC to stop',0a,0d,'$'