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IBMRS232.ASM
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Assembly Source File
|
1986-12-29
|
24KB
|
674 lines
page 60,132
;***********************************************************
;** **
;** Device Driver for RS232 communications **
;** IBM PC Version **
;** Copyright (C) Texas Instruments 1986 **
;** Author: Greg Haley **
;** **
;** THIS SOURCE CODE MAY BE DISTRIBUTED AND MODIFIED **
;** ONLY IF THE ORIGINAL COPYRIGHT AND AUTHOR CREDITS **
;** REMAIN INTACT. **
;** **
;** Project Start Date: 11/20/86 **
;** **
;** Re: 12/29/86 by Greg Haley **
;** Added send_xon routine. **
;** Added 19200 baud. **
;** **
;***********************************************************
name ibmrs232
title Device Driver for IBM PC Communications
code segment byte
assume cs:code,ds:nothing,es:nothing
include rs232.inc
page
;***********************************************************
;** Keyboard Routines **
;***********************************************************
keyboard equ 22 ; IBM PC keyboard INT
altah db 0 ; Storage for high byte of key input
k_ready:
mov al,cs:altah ; Get 2nd half of F-key?
or al,al
jnz k_rdy_xit ; Yes, skip to end
mov ah,1 ; Is a char waiting?
int keyboard
jz k_rdy_xit ; No, exit
or ax,ax ; If it was a ^C, remove it
jnz k_rdy_xit
xor ah,ah
int keyboard
jmp short k_ready ; And try again
k_rdy_xit:
ret
k_read:
xor ax,ax ; Clear AX
xchg al,cs:altah ; Get 2nd half of F-key?
or al,al
jnz k_r_xit ; Yes, skip to end
k_r_1:
xor ah,ah
int keyboard
or ax,ax ; Was it a ^C?
jz k_r_1 ; Yes, get another
or al,al ; Is it a F-key?
jnz k_r_xit ; No, exit
mov cs:altah,ah ; Yes, save 2nd half
k_r_xit:
ret
page
;***********************************************************
;** Communications Routines **
;***********************************************************
recv_size equ 800h ; Receive buffer size
; Must be one of these values:
; 0004h = 4 bytes
; 0008h = 8 bytes
; 0010h = 16 bytes
; 0020h = 32 bytes
; 0040h = 64 bytes
; 0080h = 128 bytes
; 0100h = 256 bytes
; 0200h = 512 bytes
; 0400h = 1024 bytes
; 0800h = 2048 bytes
; 1000h = 4096 bytes
; 2000h = 8192 bytes
; 4000h = 16384 bytes
; 8000h = 32768 bytes
recv_limit equ not recv_size ; Receive buffer limit mask
busy_len equ recv_size *3 /4 ; Go busy at 3/4 buf length
not_busy_len equ recv_size /2 ; Not busy at 1/2 buf length
int_controller equ 21h ; 8259A Interrupt Controller port
int_ack equ 20h ; 8259A Interrupt Acknowledge port
enable_ints equ 00001111b ; Enable interrupts
disable_ints equ 00000000b ; Disable interrupts
dcd_bit equ 128 ; DCD bit in modem status register
cts_bit equ 16 ; CTS bit in modem status register
dsr_bit equ 32 ; DSR bit in modem status register
ri_bit equ 64 ; RI bit in modem status register
dtr_rts_out2 equ 00001011b ; DTR, RTS, & OUT2
no_dlab equ 01111111b ; Mask off DLAB bit
char_waiting equ 00000001b ; Receive buffer full bit
int_pending equ 00000001b ; Int pending bit in 8250
xon equ 11h ; xmit on busy char
xoff equ 13h ; xmit off busy char
page
;***********************************************************
;** Variables **
;***********************************************************
old_ss dw 0 ; Old SS reg
old_sp dw 0 ; Old SP reg
db 80 dup (?) ; Stack
i_stack label byte
rq_head dw 0 ; Receive Queue start
rq_tail dw 0 ; Receive Queue stop
rq_len dw 0 ; Current receive Queue length
rqueue db recv_size dup (?) ; Receive queue
oldseg dw 0 ; Old segment for int vector
oldoff dw 0 ; Old offset for int vector
busy_hand db 0 ; busy handling type
r_busy db 0 ; recv busy flag
t_busy db 0 ; xmit busy flag
xmit_busy db 0 ; xmit busy flag (for ints)
m_stat db 0 ; Current modem status
l_stat db 0 ; Current line status
dcw dw 1100000001010000b ; default 2400, 8, N, 1
parity_on db 0 ; Parity flag
int_tbl dw mod_stat ; Interrupt branch table
dw xmit_mt
dw rec_full
dw lin_stat
; table for baud rate constants
baud_tbl dw 417h ; 110
dw 300h ; 150
dw 180h ; 300
dw 0c0h ; 600
dw 60h ; 1200
dw 30h ; 2400
dw 18h ; 4800
dw 0ch ; 9600
speed dw 0030h ; Baud rate to use (2400)
comm_parms db 10000011b ; No parity, 8 data, 1 stop
; table for port number init tables
p_table dw port1_tbl
dw port2_tbl
port_n dw port1_tbl ; default port is 1
; port 1 init table
port1_tbl dw 0ch ; Interrupt vector for irq
db 11101111b ; Mask to enable irq
db 00010000b ; Mask to unable irq
dw 3f8h ; Receive buffer port
dw 3f8h ; Transmit buffer port
dw 3f8h ; Divisor least significant byte
dw 3f9h ; Divisor most significant byte
dw 3fbh ; 8250 UART Control port
dw 3fdh ; 8250 UART Status port
dw 3fch ; 8250 Modem Control port
dw 3feh ; 8250 Modem Status port
dw 3f9h ; 8250 interrupt enable register
dw 3fah ; 8250 interrupt ack register
db 64h ; 8259 Specific EOI
p_tbl_size equ $-port1_tbl
; port 2 init table
port2_tbl dw 0bh ; Interrupt vector for irq
db 11110111b ; Mask to enable irq
db 00001000b ; Mask to unable irq
dw 2f8h ; Receive buffer port
dw 2f8h ; Transmit buffer port
dw 2f8h ; Divisor least significant byte
dw 2f9h ; Divisor most significant byte
dw 2fbh ; 8250 UART Control port
dw 2fdh ; 8250 UART Status port
dw 2fch ; 8250 Modem Control port
dw 2feh ; 8250 Modem Status port
dw 2f9h ; 8250 interrupt enable register
dw 2fah ; 8250 interrupt ack register
db 63h ; 8259 Specific EOI
; defaults for port 1
port_tbl label word
comm1_vector dw 0ch ; Interrupt vector for irq
irq_enab_mask db 11101111b ; Mask to enable irq
irq_unab_mask db 00010000b ; Mask to unable irq
recv_buffer dw 3f8h ; Receive buffer port
send_buffer dw 3f8h ; Transmit buffer port
lsb_divisor dw 3f8h ; Divisor least significant byte
msb_divisor dw 3f9h ; Divisor most significant byte
line_control dw 3fbh ; 8250 UART Control port
line_status dw 3fdh ; 8250 UART Status port
modem_control dw 3fch ; 8250 Modem Control port
modem_status dw 3feh ; 8250 Modem Status port
int_enable dw 3f9h ; 8250 interrupt enable register
int_id dw 3fah ; 8250 interrupt ID register
SEOI db 64h ; 8259 Specific EOI
page
;***********************************************************
;** Subroutine to set up comm chip per the DCW **
;** DCW is in AX **
;***********************************************************
set_dcw:
; clear comm parms
xor dl,dl
; set parity type
mov bl,al ; get low byte in BL
and bl,00000011b ; mask unused bits
or dl,bl ; change parity
mov cl,3
shl dl,cl
and bl,00000001b ; change parity flag
mov parity_on,bl ;
; set num stop bits
mov bl,al ; get low byte in BL
and bl,00001000b ; mask unused bits
shr bl,1
or dl,bl
; set data bits
mov bl,ah ; get high byte in BL
and bl,01000000b ; mask unused bits
or bl,10000000b
mov cl,6
shr bl,cl
or dl,bl
; Save comm parms
mov comm_parms,dl
; set baud rate
mov bl,al ; get low byte in BL
and bl,01110000b ; mask unused bits
mov cl,3 ; shift to make word ptr
shr bl,cl
mov si,offset baud_tbl ; point to baud table
xor bh,bh ; make BX a byte ptr
add si,bx ; SI now points to baud rate const
mov dx,word ptr [si] ; get baud rate in DX
mov speed,dx ; save baud rate
; set busy type
mov bl,ah
and bl,00000011b ; mask unwanted bits
mov byte ptr busy_hand,bl ; store it
; set port number
mov bl,ah ; get high byte in BL
and bl,00001000b ; mask unused bits
shr bl,1 ; shift to make word ptr
shr bl,1
mov si,offset p_table ; point to port table
xor bh,bh ; make BX a byte ptr
add si,bx ; SI now points to baud rate const
mov dx,word ptr [si] ; get port adrs in DX
mov word ptr port_n,dx ; save port number adrs
ret
page
;***********************************************************
;** Subroutine to set up interrupt vector **
;** and initialize the 8250 comm chip **
;***********************************************************
init_comm:
push ds
push cs
pop ds
; get correct port parameters
push es
push cs
pop es
mov si,word ptr port_n ; get port table adrs
mov di,offset port_tbl ; DI points to table to use
mov cx,p_tbl_size ; CX has table length
repz movsb ; move it
pop es
; Save old int vector for irq
mov di,comm1_vector
call get_vector
mov word ptr oldseg,bx
mov word ptr oldoff,dx
; Set up int vector for irq
push cs ; Make BX = CS
pop bx
mov dx,offset isr
mov di,comm1_vector
call set_vector
; Enable irq from 8259A
cli
in al,int_controller
jmp $+2 ; delay
and al,irq_enab_mask
out int_controller,al
; Set baud rate, parity, etc.
mov dx,line_control
mov al,comm_parms
out dx,al
mov dx,lsb_divisor
mov ax,speed
out dx,al
mov dx,msb_divisor
mov al,ah
out dx,al
mov dx,line_control
in al,dx
and al,no_dlab
out dx,al
; Read receive buffer register
call lin_stat
test al,char_waiting
jz init_1
mov dx,recv_buffer
in al,dx
init_1:
; Read modem control register
mov dx,modem_control
in al,dx
; Read modem status register
call mod_stat
; Read UART status register
call lin_stat
; Enable 8250 interrupts
mov dx,line_control
in al,dx
and al,no_dlab
out dx,al
mov dx,int_enable
mov al,enable_ints
out dx,al
; Raise DTR, RTS, & OUT2
mov dx,modem_control
mov al,dtr_rts_out2
out dx,al
pop ds
sti
ret
page
;***********************************************************
;** Subroutine to restore interrupt vector **
;** and reset the 8250 comm chip **
;***********************************************************
de_init:
cli
; Disable irq
in al,int_controller
or al,cs:byte ptr irq_unab_mask
jmp $+2 ; delay
jmp $+2 ; delay
out int_controller,al
; Disable interrupts on 8250 and drop DTR, RTS
mov dx,cs:line_control
in al,dx
jmp $+2 ; delay
and al,no_dlab
out dx,al
mov dx,cs:int_enable
xor al,al
out dx,al
; It's probably not a good idea to restore the vector at close in
; this case, but here's the code to do it:
;
; Restore int vector for irq
; mov bx,cs:word ptr oldseg
; mov dx,cs:word ptr oldoff
; mov di,comm1_vector
; call set_vector
sti
ret
page
;***********************************************************
;** Interrupt Service Routine **
;***********************************************************
isr:
cli
cld
; Set up new stack
mov cs:word ptr old_sp,sp
mov cs:word ptr old_ss,ss
mov sp,cs
mov ss,sp
mov sp,offset i_stack
push ax
push bx
push cx
push dx
push ds
push cs
pop ds
; Verify int came from 8250
mov dx,int_id
in al,dx
test al,int_pending
jnz isr_exit
; Branch to correct routine
cbw ; make int type a word
mov bx,offset int_tbl ; point to int table
add bx,ax ; add int type
sti
call cs:word ptr [bx] ; go do subroutine
cli
isr_exit:
; Tell 8259A we're done
mov al,SEOI
out int_ack,al
pop ds
pop dx
pop cx
pop bx
pop ax
; restore stack
mov ss,cs:word ptr old_ss
mov sp,cs:word ptr old_sp
sti
iret
page
;***********************************************************
;** Subroutine to read the modem status **
;***********************************************************
mod_stat:
mov dx,modem_status ; Read modem status (CHB)
in al,dx ; into reg AL
xor ah,ah
test al,ri_bit
jz test_dsr
or ah,4
test_dsr:
test al,dsr_bit
jz test_cts
or ah,1
test_cts:
shl ah,1
test al,cts_bit
jz test_dcd
or ah,1
test_dcd:
shl ah,1
test al,dcd_bit
jz test_done
or ah,1
test_done:
; AH now contains the line signals
; ---------------------------------
; | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
; ---------------------------------
; | | | | RI| |DSR|CTS|DCD|
; ---------------------------------
; 0=down, 1=up
mov cs:byte ptr m_stat,ah ; Update current modem status
; Check for busy handling
shr ah,1 ; DSR in bit 0
shr ah,1
cmp cs:byte ptr busy_hand,2 ; DSR busy handling?
jne xit_mod_stat ; No, skip
mov al,ah ; save AH
set_tbusy:
and al,1 ; up = busy on
; not al ; down = busy on
mov cs:byte ptr t_busy,al ; set busy
xit_mod_stat:
ret
page
;***********************************************************
;** Subroutine to send the next char in queue **
;***********************************************************
xmit_mt:
mov cs:byte ptr xmit_busy,0 ; We're not busy
ret
page
;***********************************************************
;** Subroutine to receive a char and queue it **
;***********************************************************
rec_full:
mov dx,recv_buffer ; Get char
in al,dx
cmp cs:byte ptr parity_on,0 ; parity?
jz no_par ; No, don't mask off parity bit
and al,7fh ; Yes, mask off parity bit
no_par:
; check for XON-XOFF busy char
cmp cs:byte ptr busy_hand,3 ; XON-XOFF busy handling?
jne queue_char ; No, skip busy handling
cmp al,xoff ; Need to set busy?
jne chk_r_xon ; No, skip
mov cs:byte ptr t_busy,1 ; set busy
jmp xit_rec_full ; We're done
chk_r_xon:
cmp al,xon ; Need to reset busy?
jne queue_char ; No, skip busy handling
mov cs:byte ptr t_busy,0 ; reset busy
jmp xit_rec_full ; We're done
queue_char:
; check for buffer overflow
cmp cs:word ptr rq_len,recv_limit ; buffer full?
jb buf_full1 ; No, skip
inc cs:word ptr rq_tail ; Yes, lose 1 char
and cs:word ptr rq_tail,recv_limit
dec cs:word ptr rq_len ; Adjust queue length
buf_full1:
mov bx,offset rqueue ; Queue char
mov dx,cs:word ptr rq_head
add bx,dx
mov cs:byte ptr [bx],al
inc dx
and dx,recv_limit ; wrap if >= receive size
mov cs:word ptr rq_head,dx
inc cs:word ptr rq_len ; Adjust queue length
; set busy if needed
cmp cs:byte ptr busy_hand,3 ; XON-XOFF busy handling?
jne set_rb_done ; No, skip
cmp cs:word ptr rq_len,busy_len ; Need to set busy?
jb set_rb_done ; No, skip
mov cs:byte ptr r_busy,1 ; set busy flag
mov dx,cs:word ptr send_buffer ; send XOFF char
mov al,xoff
out dx,al
set_rb_done:
xit_rec_full:
ret
page
;***********************************************************
;** Subroutine to send an xon char if needed **
;***********************************************************
send_xon:
cmp cs:byte ptr busy_hand,3 ; XON-XOFF busy handling?
jne xit_send_xon ; No, skip
mov dx,cs:word ptr send_buffer ; send XOFF char
mov al,xon
out dx,al
xit_send_xon:
ret
page
;***********************************************************
;** Subroutine to read the line status **
;***********************************************************
lin_stat:
mov dx,line_status
in al,dx ; read status
mov cs:byte ptr l_stat,al ; Update current line status
ret
page
;***********************************************************
;** Subroutine to get an interrupt vector **
;** **
;** di = vector number **
;** **
;** Return: **
;** bx = segment **
;** dx = offset **
;***********************************************************
get_vector:
push es
xor ax,ax
mov es,ax
shl di,1
shl di,1
mov dx,es:word ptr[di]
mov bx,es:word ptr[di+2]
pop es
ret
page
;***********************************************************
;** Subroutine to set an interrupt vector **
;** **
;** di = vector number **
;** bx = segment **
;** dx = offset **
;***********************************************************
set_vector:
push es
xor ax,ax
mov es,ax
shl di,1
shl di,1
mov es:word ptr[di],dx
mov es:word ptr[di+2],bx
pop es
ret
page
;***********************************************************
;** Everything past here is truncated after install **
;***********************************************************
init proc near
lds bx,cs:[ptrsav]
mov word ptr [bx].trans,offset init ;set break address
mov [bx].trans+2,cs
push cs
pop ds
mov dx,offset init_msg
mov ah,9
int 21h
jmp exit
init endp
init_msg:
db cr,lf,'IBM PC Communications Driver v2.51'
db ' Copyright (C) Texas Instruments 1986'
db cr,lf,'Written by '
db 'Greg Haley'
db cr,lf,cr,lf,'$'
code ends
end
