comment *

    SERTYPE.ASM

    Purpose:

    Determines the type of UART in each serial port



    Author:

    Douglas Boling, in PcMag. With some modifications by Yousuf Khan.

*



dosseg



bdseg   segment at 40h  ;bios data segment

        com1    dw      ?

        com2    dw      ?

        com3    dw      ?

        com4    dw      ?

        ends



_data   segment para 'data'

        uart1   db      0

        uart2   db      0

        uart3   db      0

        uart4   db      0

        portmsg db      "COMx: $"

        x8250   db      "NS 8250 (non-FIFO)",13,10,"$"

        x16450  db      "NS 8250A/16450/16550 (non-FIFO)",13,10,"$"

        xfifo   db      "NS 16550A/Intel 82510 (FIFO)",13,10,"$"

        xdma    db      "IBM type 3 (FIFO/DMA)",13,10,"$"

        pas_de_ports    db      "No serial ports detected",13,10,"$"

        ends



_stack  segment para stack 'stack'

        db      200h dup (?)

        ends



cseg    segment para 'code'

        mov     ax, bdseg

        mov     es, ax          ;ES := Bdseg

        mov     ax, _data

        mov     ds, ax          ;DS := _data

        assume  cs:cseg, ds:_data, es:bdseg, ss:_stack

        xor     al, al          ;# of serial ports = 0

        mov     dx, [com1]

        cmp     dx, 0

        je      eoproc

        inc     al              ;# of serial ports = 1

        push    ax

        call    uartdet

        mov     [uart1], al     ;remember the type of this UART

        pop     ax

        mov     dx, [com2]

        cmp     dx, 0

        je      eoproc

        inc     al              ;# of serial ports = 2

        push    ax

        call    uartdet

        mov     [uart2], al

        pop     ax

        mov     dx, [com3]

        cmp     dx, 0

        je      eoproc

        inc     al              ;# of serial ports = 3

        push    ax

        call    uartdet

        mov     [uart3], al

        pop     ax

        mov     dx, [com4]

        cmp     dx, 0

        je      eoproc

        inc     al              ;# of serial ports = 4

        push    ax

        call    uartdet

        mov     [uart4], al

        pop     ax



eoproc:

        call    disp

        mov     ah, 4ch

        int     21h



delay   macro

        jmp     $ 2

        endm



uartdet proc    near

        push    bx

        push    cx

        mov     bx, dx          ;save starting i/o addr

        add     dx, 4           ;point to modem ctrl reg

        in      al, dx          ;disable interrupts

        push    ax

        and     al, 11111011b

        out     dx, al

        mov     ch, 0           ;assume type 0

        mov     dx, bx

        add     dx, 7           ;see if scratch reg exists

        mov     al, 55h

        cli

        out     dx, al          ;write to scratch reg

        delay

        in      al, dx          ;read back

        cmp     al, 55h

        jne     endudet

        mov     al, 0AAh

        out     dx, al          ;write to scratch reg

        delay

        in      al, dx          ;read back

        sti

        cmp     al, 0AAh

        jne     endudet

        inc     ch              ;assume type 1

        mov     dx, bx

        add     dx, 2           ;point to FIFO ctrl reg

        mov     al, 7           ;attempt to enable FIFOs

        cli

        out     dx, al

        delay

        in      al, dx          ;read interrupt ID reg

        sti

        and     al, 0c0h        ;strip all but FIFO bits

        jz      endudet         ;if bits 0, 16450/16550

        inc     ch              ;assume type 2

        mov     dx, bx

        add     dx, 8003h       ;point to enhanced reg 1

        cli

        in      al, dx

        push    ax

        or      al, 01000000b   ;enable DMA transmission

        out     dx, al

        push    dx

        mov     dx, bx

        add     dx, 2

        in      al, dx

        mov     cl, al

        pop     dx              ;restore enhanced reg 1

        pop     ax

        out     dx, al

        sti

        and     cl, 0c0h        ;again mask all but FIFO ID

        cmp     cl, 40h

        jne     endudet         ;must be type 2 (FIFO)

        inc     ch              ;must be type 3 (DMA)



endudet:

        pop     ax

        mov     dx, bx

        add     dx, 4           ;point to modem ctrl reg

        out     dx, al          ;restore initial condition

        xor     ax, ax

        mov     al, ch

        mov     dx, bx

        pop     cx

        pop     bx

        ret

uartdet endp



disp    proc    near

        push    ax      ;save AX

        cmp     al, 0   ;no serial ports?

        je      noports

        mov     bx, offset ds:[uart1]   ;offset of UART type field

        mov     di, offset ds:[portmsg][3] ;offset of 4th char in message

        mov     cx, 0

        mov     cl, al  ;number of iterations



@l1:

        ;

        ;write "COMx: " message substituting "x" for proper comport #

        ;

        mov     dl, 4

        sub     dl, cl

        add     dl, 30h ;convert to ASCII number

        mov     [di], dl

        lea     dx, portmsg

        mov     ah, 9

        int     21h

        ;

        ;write the UART type now

        ;

        mov     dl, [bx]

        cmp     dl, 0

        jne     @t2

        lea     dx, x8250

        mov     ah, 9

        int     21h

        jmp     @eot



@t2:    cmp     dl, 1

        jne     @t3

        lea     dx, x16450

        mov     ah, 9

        int     21h

        jmp     @eot



@t3:    cmp     dl, 2

        jne     @t4

        lea     dx, xfifo

        mov     ah, 9

        int     21h

        jmp     @eot



@t4:    lea     dx, xdma

        mov     ah, 9

        int     21h



@eot:   inc     bx

        loop    @l1

        jmp     eoproc2



noports:

        lea     dx, pas_de_ports

        mov     ah, 9

        int     21h



eoproc2:

        pop     ax

        ret

disp    endp



        ends

        end



; EOF SERTYPE.ASM