Shareware Grab Bag

home *** CD-ROM | disk | FTP | other *** search

/ Shareware Grab Bag / Shareware Grab Bag.iso / 007 / simcode.arc / COM.ASM < prev next >

Wrap

Assembly Source File | 1984-12-12 | 19.0 KB | 772 lines

Title COM - Interrupt Driven Communications Software Page 86,132 include struct.mac ;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ;: :: ;: Copyright, 1982, University of B.C. Computing Centre :: ;: :: ;: Permission to copy without fee all or part of this :: ;: material is granted provided that copies are not :: ;: made or distributed for direct commercial advantage, :: ;: and that this copyright notice is retained in the copy. :: ;: :: ;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ;: :: ;: Modified for use with SIMTERM and PASCAL calling sequences :: ;: Functions added for controlling and examining line status. :: ;: Modified to use the 'structured' macros for easier reading. :: ;: :: ;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: Name DRIVERS ;8250 Asynchronous Communications Element - Registers ; The following EQUs assume that the base address is ; in BX. DLH EQU [bx+1] ;Divisor Latch High byte DLL EQU [bx] ;Divisor Latch Low byte IER EQU [bx+1] ;Interrupt Enable Register IIR EQU [bx+2] ;Interrupt Identification Register IOR EQU [bx] ;Input Output Register LCR EQU [bx+3] ;Line Control Register LSR EQU [bx+5] ;Line Status Register MCR EQU [bx+4] ;Modem Control Register MSR EQU [bx+6] ;Modem Status Register rs232_base equ 400H ;address of rs232 adapters ;8259A Priority Interrupt Controller - Registers INTA0 EQU 20H ;Register 0 INTA1 EQU 21H ;Register 1 ;8259A Priority Interrupt Controller - Commands EOI EQU 20H ;Non-specific EOI timer_low equ es:[46CH] ; low word of timer ;COM Flags Mask Bits F_T_ACT EQU 00000001B ;Transmitter Active ;F_BREAK EQU 00000010B ;Break sequence started F_XCONT EQU 00000100B ;XON/XOFF control enabled F_XOFFR EQU 00001000B ;XOFF recieved/don't transmit F_XOFFT EQU 00010000B ;XOFF transmitted/drain buffer F_SXOFF EQU 00100000B ;Send XOFF F_SXON EQU 01000000B ;Send XON ;Constants RBUF_SIZE EQU 3000 ;Receive buffer size FENCE_1 EQU rbuf_size/4 ;Send XON fence FENCE_2 EQU 1000 ;Send XOFF fence SET_BRK EQU 01000000B ;Set-Break flag of LCR thre equ 00100000b ; THRE in LSR XOFF EQU 00010011B ;ASCII DC3 XON EQU 00010001B ;ASCII DC1 ;ERR_FLAG masks chg_lsr equ 00001B ; change in LSR chg_msr equ 00010B ; change in MSR buf_ful equ 00100B ; receive buffer full trans_error equ 01000B ; got an xmit interrupt when we should not have not_xmitted equ 10000B ; could not transmit character data segment public 'data' public err_flag err_flag db 0 ; record any error conditions public lsr_value lsr_value db ? ; LSR at change public msr_value msr_value db ? ; MSR at change public recv_reset recv_reset db 0 ; flag to reset receiver buffer on BREAK data ends dgroup group data Communications SEGMENT PARA PUBLIC 'CODE' com_base dw ? ; base address of the Async Port irq_num db ? ; user specified IRQ int_base dw ? ; interrupt @ corresonding to IRQ ds_pascal dw ? ; DS on entry (PASCAL Data segment) CIVA DW ? ;Comm Interrupt Vector Address CIVS DW ? ;Comm Interrupt Vector Segment FLAGS DB ? ;COM state Flags intr_count dw 0 ; count # of double interrupts R_INDEX DW ? ;Recieve buffer index pointer R_length DW ? ;Recieve buffer length R_BUFF DB rbuf_size DUP(?) ;Recieve character Buffer r_buff_end equ $-1 PUBLIC COM_Begin,COM_End PUBLIC breaker PUBLIC COM_Get PUBLIC send ;--------------------------------------- ; Setup the interrupt code ;--------------------------------------- COM_Begin PROC FAR ASSUME CS:Communications,DS:nothing ;procedure COM_Begin( Port : word; [bp+12] (IRQ [bp+13]) ; Speed : word; [bp+10] ; LCR : word; [bp+8] ; X_Control : boolean ); [bp+6] PUSH BP ;Save frame pointer MOV BP,SP ;Get new frame pointer mov ax,ds mov ds_pascal,ax ; Save DS to PASCAL data segment push ds mov ax,cs ;setup DS addressability mov ds,ax assume ds:communications XOR AX,AX ;Clear AX MOV ES,AX ;Address bottom of memory MOV FLAGS,AL ;Initialize state flags MOV R_length,AX ;Zero Receive buffer Length MOV R_INDEX,OFFSET R_BUFF mov si,[bp+12] ; com port # and si,0FFH ; mask off the port# shl si,1 mov bx,es:rs232_base[si] ; pickup the base address mov com_base,bx ; save for the rest of the program MOV AL,10000000B ;Set Divisor-Latch bit lea dx,lcr OUT DX,AL ;Write LCR MOV AX,[BP+10] ;Get Bit Rate Divisor lea dx,dll OUT DX,AL ;Write Divisor Latch Low byte MOV AL,AH ;Get high part of divisor lea DX,DLH OUT DX,AL ;Write Divisor Latch High byte MOV AL,[BP+8] ;Get Line Control Register settings AND AL,00111111B ;Mask out unwanted stuff lea DX,LCR OUT DX,AL ;Write LCR .if <byte ptr [bp+6]> ne 0 OR FLAGS,F_XCONT ;Turn on XON/XOFF control .endif mov al,[bp+13] ; user specified IRQ xor ah,ah ; clear high byte shl ax,1 shl ax,1 ; X 4 mov si,ax add si,20H ; base of 8259A interrupts mov int_base,si ; save it CLI ;Disable interrupts MOV AX,ES:[si+2] ;Get CIV segment MOV CIVS,AX ;Save CIVS MOV AX,ES:[si] ;Get CIV address MOV CIVA,AX ;Save CIVA MOV ES:[si+2],CS ;Patch Interrupt Vector MOV WORD PTR ES:[si],OFFSET COM_I STI ;Enable interrupts MOV AL,00001011B ;Modem Control Register Settings lea DX,MCR OUT DX,AL ;Write MCR lea DX,MSR ;Get address of Modem Status Register IN AL,DX ;Get Modem Status lea DX,LSR ;Get address of Line Status Register IN AL,DX ;Get Line Status lea DX,IOR ;Get address of I/O Register IN AL,DX ;Get spurious reciever data MOV AL,00001101B ;Interrupt Enable Register Settings ; Don't enable the THRE interrupt lea DX,IER OUT DX,AL ;Write IER mov cl,[bp+13] ; user specified IRQ mov ch,1 ; bit for mask shl ch,cl ; shift mask to proper position mov irq_num,ch ; save it not ch ; complement IN AL,INTA1 ;Get IRQ mask from 8259A AND AL,ch ;Mask out IRQ4 bit OUT INTA1,AL ;Enable IRQ4 pop ds POP BP ;Restore Frame Pointer RET 8 ;Return to caller COM_Begin ENDP ;--------------------------------------- ; reset to original condition before exit ;--------------------------------------- COM_End PROC FAR ;procedure COM_End; push ds mov ax,cs ;setup addressability for DS mov ds,ax mov bx,com_base XOR AX,AX ;Clear AX lea DX,IER OUT DX,AL ;Turn off comm interrupts IN AL,INTA1 ;Get 8259A IRQ mask OR AL,irq_num ;Mask in IRQ4 bit OUT INTA1,AL ;Disable IRQ4 XOR AX,AX ;Clear AX MOV ES,AX ;Address bottom of mermory CLI ;Disable interrupts mov si,int_base MOV AX,CIVS ;Restore Comm Interrupt Vector MOV ES:[si+2],AX MOV AX,CIVA MOV ES:[si],AX STI ;Enable interrupts pop ds RET ;Return to caller COM_End ENDP ;--------------------------------------- ; interrupt code ;--------------------------------------- COM_I PROC FAR ;COM Interrupt service routine ;--------------------- removed to `cure' the overrun problem ------------+ ; STI ;Allow further interrupts | ;------------------------------------------------------------------------+ PUSH AX PUSH BX PUSH DX PUSH DI PUSH DS mov ax,cs ;setup addressability for DS mov ds,ax mov bx,com_base dec intr_count ; ; loop back here to see if any move interrupts are pending ; retry: lea DX,IIR IN AL,DX ;Get class of interrupt .ifc al,1 *LONG* ; interrupt pending inc intr_count xor ah,ah ; clear high bits mov di,ax jmp [intr_type+di] ; -------------------- ; Interuupt Jump Table ; -------------------- intr_type dw modem_intr dw trans_intr ; should not get here!! dw recv_intr dw status_intr ; --------------------- ; LINE STATUS INTERRUPT ; --------------------- status_intr: push ds mov ax,ds_pascal mov ds,ax assume ds:dgroup lea DX,LSR ;Get line status IN AL,DX mov lsr_value,al ;save value at change or err_flag,chg_lsr pop ds assume ds:communications JMP retry ; ---------------------------- ; RECEIVE DATA READY INTERRUPT ; ---------------------------- recv_intr: lea DX,IOR ;Get address of I/O Register IN AL,DX ;Get recieved byte .ifs flags,f_xcont ; XON/XOFF control mov ah,al ; mask off the parity and ah,7FH ; bit on the character .if ah e xoff OR FLAGS,F_XOFFR ;To stop transmitter JMP retry .endif .if ah e xon ; XON received AND FLAGS,NOT F_XOFFR ;To release transmitter JMP retry .endif .if r_length g <size r_buff - fence_2> ; if recv buffer is full .ifc flags,f_xofft ; and XOFF not transmitted .ifs flags,f_t_act ; xmitter not active or flags,f_sxoff+f_xofft ; send XOFF .else or flags,f_xofft push ax mov al,xoff ; send the XOFF character call send_char pop ax .endif .endif .endif .endif .if r_length ge <size r_buff> ;if buffer full, ignore character push ds mov ax,ds_pascal mov ds,ax assume ds:dgroup or err_flag,buf_ful pop ds assume ds:communications jmp retry .endif MOV DI,R_INDEX ;Get pointer into R_BUFF MOV [DI],AL ;Put new byte into buffer INC R_length ;Increase buffer length by 1 byte inc r_index .if di e <offset r_buff_end> ;check for wrap around mov r_index,offset r_buff .endif jmp retry ; --------------------- ; TRANSMITTER INTERRUPT (Should never get here. If we do, exit gracefully) ; --------------------- trans_intr: push ds mov ax,ds_pascal mov ds,ax assume ds:dgroup or err_flag,trans_error pop ds assume ds:communications jmp retry ; ---------------------- ; MODEM STATUS INTERRUPT ; ---------------------- modem_intr: push ds mov ax,cs:ds_pascal mov ds,ax assume ds:dgroup lea DX,MSR ;Get modem status IN AL,DX mov msr_value,al or err_flag,chg_msr pop ds assume ds:communications jmp retry ; loop until all interrupts are cleared .endif ; CLI ;Turn off interrupts MOV AL,EOI ;End Of Interrupt command OUT INTA0,AL ;Signal 8259A of EOI POP DS POP DI POP DX POP BX POP AX IRET COM_I ENDP ;--------------------------------------- ; Generate BREAK ;--------------------------------------- breaker PROC FAR assume ds:nothing ;procedure COM_Break; mov bx,com_base cli ; lock out interrupts lea dx,lcr IN AL,DX ;Get LCR settings OR AL,SET_BRK ;Set set-break flag OUT DX,AL ;Start break sequence and flags,not f_t_act+f_xoffr ; mark xmitter `not active' assume es:nothing sti XOR AX,AX ;Clear AX mov es,ax ; ES points to low core mov ax,timer_low ; pickup current time .repeat ; wait for time to expire mov cx,timer_low sub cx,ax .until cx a 2 cli in al,dx and al,not set_brk ; stop the break sequence out dx,al mov ax,ds_pascal ; setup ES->PASCAL data segment mov es,ax assume es:dgroup .if recv_reset ne 0 mov r_length,0 ; reset the receiver buffer .endif assume es:nothing sti RET ;Return to caller breaker ENDP ;--------------------------------------- ; clear the receiver buffer ;--------------------------------------- public clear_receiver clear_receiver proc far assume ds:nothing mov ax,ds_pascal mov es,ax assume es:dgroup .if recv_reset ne 0 cli mov r_length,0 ; clear the recv buffer sti .endif assume es:nothing ret clear_receiver endp ;--------------------------------------- ; Get character from receive buffer ;--------------------------------------- COM_Get PROC FAR assume ds:nothing ;function COM_Get( var Character : char ) : boolean .if r_length le 0 ; receive buffer is empty MOV AX,1 ;Return buffer empty code to caller RET 2 .endif PUSH BP ;Save frame pointer MOV BP,SP ;Get new frame pointer push ds mov ax,ds ;setup ES to point to PASCAL data space mov es,ax mov ax,cs ;setup addressability for DS mov ds,ax assume ds:communications mov bx,com_base CLI ;Disable interrupts MOV SI,R_INDEX ;Get pointer into recieve buffer SUB SI,R_length ;Subtract length of buffer .if si l <offset r_buff> ; check if pointer needs adjustment add si,size r_buff .endif MOV AL,[SI] ;Get character from buffer DEC R_length ;Reduce size of buffer by 1 byte MOV DI,[BP+6] ;Get address of parameter MOV es:[DI],AL ;Store result of COM Get .ifs flags,f_xcont ;XON/XOFF control specified .ifs flags,f_xofft ;XOFF was transmitted .if r_length le fence_1 ;buffer is below the low water mark AND FLAGS,NOT F_XOFFT ;Clear XOFF-transmitted flag call set_active ; set XMIT active mov al,xon ; send XON call send_char call clear_active ; clear XMIT active .endif .endif .endif XOR AX,AX ;Return O.K. code to caller STI ;Enable interrupts pop ds POP BP ;Restore frame pointer RET 2 ;Return to caller COM_Get ENDP ;--------------------------------------- ; Send a character ;--------------------------------------- send PROC FAR ;function send( Buffer : lstring ) : integer; ; 8-size, 6-@ PUSH BP ;Save frame pointer MOV BP,SP ;Get new frame pointer mov ax,ds ;save DS in ES mov es,ax push ds mov ax,cs ;setup addressability for DS mov ds,ax assume ds:communications mov bx,com_base MOV CX,[BP+8] ;Get length of string to write .if cx g 0 mov si,[bp+6] ; @ of output string .repeat call set_active mov al,es:[si] ; pickup data from PASCAL call send_char inc si call clear_active .until loop .endif mov ax,-1 ; return OK status pop ds POP BP ;Restore frame pointer RET 4 ;Return to caller send ENDP ;--------------------------------------- ; Set the transmitter active flag ;--------------------------------------- set_active proc near cli or flags,f_t_act sti ret set_active endp ;--------------------------------------- ; clear the xmit active flag and check for special conditions ;--------------------------------------- clear_active proc near cli .ifs flags,f_sxoff ; should we send an XOFF and flags,not f_sxoff sti push ax mov al,xoff call send_char pop ax jmp clear_active ; try again .endif and flags,not f_t_act sti ret clear_active endp ;--------------------------------------- ; Send a character (checking for time outs and such) ;--------------------------------------- wait_count equ 36 ; wait at most 2 seconds send_char proc near push cx push dx .ifs flags,f_xoffr ; check for xmit hold xor cx,cx mov es,cx ; address low core for the timer mov dx,timer_low ; pickup current time .repeat .ifc flags,f_xoffr ; terminate if cleared mov cx,wait_count+1 .else mov cx,timer_low sub cx,dx .endif .until cx a wait_count ; wait at most 2 seconds and flags,not f_xoffr ; clear the wait flag and just proceed .endif xor cx,cx ; setup wait counter lea dx,lsr mov ah,al ; save character to xmit .repeat in al,dx .ifs al,thre ; THRE is empty mov al,ah lea dx,ior out dx,al pop dx pop cx ret .endif .until loop push ds mov ax,ds_pascal mov ds,ax assume ds:dgroup or err_flag,not_xmitted pop ds assume ds:communications pop dx pop cx ret send_char endp ;--------------------------------------- ; get/set XON/XOFF status ;--------------------------------------- ; ; function x_cont(new : boolean) : boolean ; sets the new value for XON/XOFF control and returns the OLD value ; public x_cont assume ds:nothing x_cont proc far push bp mov bp,sp xor ax,ax ;set to FALSE cli .ifs flags,f_xcont inc ax ;set to TRUE .endif and flags,not f_xcont ;clear the flag .if <byte ptr [bp+6]> ne 0 or flags,f_xcont .endif sti pop bp ret 2 x_cont endp ;--------------------------------------- ; procedure clearterm; ; Clear the interrupt so stray data will not kill the system ;--------------------------------------- public clearterm clearterm proc far mov bx,com_base lea dx,mcr ; MCR in al,dx and al,not 1000B ; clear interrupt control bit out dx,al lea dx,ier ; IER xor al,al out dx,al ; clear all interrupts ret clearterm endp ;--------------------------------------- ; procedure dropline ; ; 'drop' the communications line ;--------------------------------------- public dropline dropline proc far mov bx,com_base lea dx,mcr in al,dx and al,0f0H ; clear the DTR and interrupt flags out dx,al ret dropline endp ;--------------------------------------- ; toggle TR -- for VENTEL autodialler ;--------------------------------------- public toggle_tr toggle_tr proc far mov bx,com_base xor ax,ax mov es,ax ; set ES to low memory lea dx,mcr in al,dx push ax ; save original value and al,0fcH ; clear the DTR and interrupt flags out dx,al mov ax,timer_low .repeat mov cx,timer_low sub cx,ax .until cx ae 18 ; wait 1 second pop ax ; retrieve original value out dx,al ret toggle_tr endp ;--------------------------------------- ; function modem_status : byte; ; ; returns the contents of the modem status register ;--------------------------------------- public modem_status modem_status proc far mov bx,com_base lea dx,msr in al,dx ret modem_status endp ;--------------------------------------- ; procedure clear_comm ; ; this resets the comm software. Will hopefully unlock any `funny' conditions ;--------------------------------------- assume ds:nothing public clear_comm clear_comm proc far cli ; lockout interrupts and flags,f_xcont ; leave the XON/XOFF set correctly mov r_length,0 mov r_index,offset r_buff sti ret clear_comm endp ;--------------------------------------- ; procedure set_interrupt_high(number:integer); ; ; This causes the communications port to have the highest priority so ; that data overruns do not occur. ;--------------------------------------- assume ds:nothing public set_interrupt_high set_interrupt_high proc far push bp mov bp,sp mov al,[bp+6] ; pick up the interrupt level add al,0C0H-1 ; setup the opcode for the 8259 out 20H,al ; do the operation pop bp ret 2 set_interrupt_high endp Communications ENDS check$ END