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Assembly Source File | 1986-12-29 | 23.2 KB | 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