.FROM: Yousuf Khan Area # 17 (Assembly Language )
.TO: Y'ALL 21 Mar 91
.SUBJECT: *.pas to *.asm
Well it seems the impossible has happened to me: I now understand
Assembler more than I understand Pascal. So I found this routine,
written in TurboPascal, that detects what type of UART you have
running. I haven't used TP in 3 years+, so I need a translation
of this pascal code to assembler, if you will:
xword:=MemW[BIOSdseg : 2 * i - 2];
Writeln('$', hex(xword, 4));
xbyte2:=Port[xword + 2];
Port[xword + 2]:=$C1;
for temp:=1 to 2 do;
xbyte3:=Port[xword + 2];
Port[xword + 2]:=xbyte2;
case ((xbyte3 and $C0) shr 6) of
0: begin
xbyte2:=Port[xword + 7];
Port[xword + 7]:=$FA;
for temp:=1 to 2 do;
if Port[xword + 7] = $FA then begin
Port[xword + 7]:=$AF;
for temp:=1 to 2 do;
if Port[xword + 7] = $AF then begin
Port[xword + 7]:=xbyte2;
Write('16450')
end
else
Write('8250')
end
else
Write('8250')
end;
1: Write('???');
2: Write('16550');
3: Write('16550A')
This is of course a routine to detect the type of UART. There are
certain things I'm having trouble understanding. BIOSdseg, is this a
variable or a built-in TPascal function? $C0 & $C1, what are these?
Yousuf Khan
* Origin: To never lose characters again (1:163/215.6)
----------------------------------------------------------------------
.FROM: Scott Canion Area # 17 (Assembly Language )
.TO: Yousuf Khan 21 Mar 91
.SUBJECT: Re: *.pas to *.asm
On 19-Mar-91, sources inform us that Yousuf Khan @ 1:163/215.6 said:
YK> Well it seems the impossible has happened to me: I now understand
YK> Assembler more than I understand Pascal.
Thanks for the pascal code, Yousuf, it is very helpful.
Here is the assembly version. I tried to keep the variables close
to the pascal source. Are you sure you have programmed in Pascal
before? :-)
================== beginning of program =============================
title "UART Detector"
page 60, 132
; comments -- the WRITE function is left up to your own implementation
; constants
BIOSdseg equ 40h ; data segment for BIOS
i equ 1 ; COM PORT (1-4)
.model tiny ; tiny model (.COM)
.code
org 100h ; .COM files start at 100h
entry:
jmp start ; jump to start of progarm
; variables
xword dw ?
xbyte2 db ?
xbyte3 db ?
jmp_table dw uart_8250_or_16450, uart_unknown, uart_16550, uart_16550a
; ------------------------ MAIN ------------------------------
start proc
mov ax, BIOSdseg
mov es, ax ; move bios data segment into ES
mov dx, es:[2*i-2] ; get offset for serial port
mov xword, dx ; xword := serial port base address
add dx, 2 ; dx := dx + 2
in al, dx ; al := port [dx]
mov xbyte2, al ; xbyte2 := al
mov al, 0c1h ; al := $C1
out dx, al ; port [dx] := al
in al, dx ; al := port [dx]
and al, 0c0h ; al := (al AND $C0)
mov cl, 5 ; cl := 5
shr al, cl ; al := (al shr 5) (5 for word jmp)
mov ah, 0 ; ah := 0
mov bp, ax ; bp := ax (al)
mov al, xbyte2 ; al := xbyte2
out dx, al ; port [dx] := al
jmp cs:[jmp_table+bp]
uart_8250_or_16450:
mov dx, xword ; dx := xword
add dx, 7 ; dx := dx + 7
in al, dx ; al := port [dx]
mov xbyte2, al ; xbyte2 := al
mov al, 0fah ; al := $FA
out dx, al ; port [dx] := al
in al, dx ; al := port [dx]
cmp al, 0fah ; if (al <> $FA)
jne uart_16450 ; then uart is 16450
mov al, 0afh ; al := $AF
out dx, al ; port [dx] := al
in al, dx ; al := port [dx]
cmp al, 0afh ; if (al <> $AF)
jne uart_8250 ; then uart is 8250
mov al, xbyte2 ; else al := xbyte2
out dx, al ; port [dx] := al
jmp uart_16450 ; uart is 16450
uart_8250:
write "8250" ; display "8250"
jmp exit
uart_16450:
write "16450" ; display "16450"
jmp exit
uart_unknown:
write "???" ; display "unknown"
jmp exit
uart_16550:
write "16550" ; display "16550"
jmp exit
uart_16550a:
write "16550A" ; display "16550A"
jmp exit
exit:
mov ax, 4c00h
int 21h ; exit to DOS
start endp ; end of proc
END entry ; end of program
====================== end of program ===============================
--- QM v1.00
* Origin: Scott's Excellent BBS HST/V.32bis (1:382/17.0)
| 
Yousuf Khan