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Assembly Source File | 1988-03-08 | 22.8 KB | 474 lines

page ,132 ;***************************************************************************** ; ; Asynchronous Support Routines ; Beispielprogramm zum Linken mit C Version 1.0 ;***************************************************************************** _TEXT SEGMENT BYTE PUBLIC 'CODE' ; Default code segment _TEXT ENDS _DATA SEGMENT WORD PUBLIC 'DATA' ; Default data segment _DATA ENDS CONST SEGMENT WORD PUBLIC 'CONST' ; Read only constants CONST ENDS _BSS SEGMENT WORD PUBLIC 'BSS' ; Uninitialized static data _BSS ENDS STACK SEGMENT PARA STACK 'STACK' ; Stack segment STACK ENDS DGROUP GROUP _DATA,CONST,_BSS,STACK _TEXT SEGMENT BYTE PUBLIC 'CODE' ASSUME CS:_TEXT,DS:DGROUP @AB EQU 4 XMITI EQU 00000h ;set to 0FFFFh for xmit via interrupt public _asnget ;get char from asynch buffer public _asnput ;put char to asynch line public _asnstat ;get status of asynch port public _asninit ;initialize asynch port & routines public _asnclr ;clear asynch receive buffer public _asnfls ;flush asynch transmit buffer public _asnexit ;remove asynch interrupt routine public _asnbaud ;set baud rate for asynch port ;***************************************************************************** ; ; POPF Macro for PC/AT 2/86 hardware bugÜ ; ;***************************************************************************** POPFF MACRO ;this kludge is due to INTEL's idiocyÜ local f1,b1 jmp short f1 ;jump over iret b1: iret ;simulate the POPF in a way that works f1: push cs ;save cs so that the IRET works correctly call b1 ;save ip and execute the IRET, and continue ENDM page ;***************************************************************************** ; ; Miscellaneous Definitions ; ;***************************************************************************** BSIZE equ 4096 ;circular receive buffer size LCRBYTE equ 00010011b ;LCR default, 8 bits+no parity ;***************************************************************************** ; ; Device address definitions ; ;***************************************************************************** PICCMD equ 20h ;8259 Priority Interrupt Controller PICMSK equ 21h ;8259 Priority Interrupt Controller ASRBR equ 008h ;8250 Receiver Buffer Register ASTHR equ 008h ;8250 Transmitter Holding Register ASDLL equ 008h ;8250 Divisor Latch Low ASDLH equ 009h ;8250 Divisor Latch High ASIER equ 009h ;8250 Interrupt Enable Register ASIIR equ 00Ah ;8250 Interrupt Identification Register ASLCR equ 00Bh ;8250 Line Control Register ASMCR equ 00Ch ;8250 Modem Control Register ASLSR equ 00Dh ;8250 Line Status Register ASMSR equ 00Eh ;8250 Modem Status Register ;***************************************************************************** ; ; data ; ;***************************************************************************** _DATA segment clock dd 115200 ;dividend value for asnbaud rbhead dw offset dgroup:rbfbeg ;recv buffer empty pointer rbtail dw offset dgroup:rbfbeg ;recv buffer fill pointer rbfbeg db BSIZE dup (?) ;recv buffer for receive data rbfend equ this byte ;recv buffer end address IF XMITI xbhead dw offset dgroup:xbfbeg ;xmit buffer empty pointer xbtail dw offset dgroup:xbfbeg ;xmit buffer fill pointer xbcnt dw BSIZE ;count of room left in buffer xbfbeg db BSIZE dup (?) ;xmit buffer for receive data xbfend equ this byte ;xmit buffer end address ENDIF iolist dw 03f0h,02f0h ;COM1, COM2 I/O base addresses ioaddr dw ? ;selected I/O adapter base address ivlist dw 0030h,002Ch ;COM1, COM2 interrupt vector addr list ivaddr dw ? ;selected interrupt vector imlist db 11101111b,11110111b ;COM1, COM2 interrupt mask list imbyte db ? ;selected interrupt mask byte _DATA ends page ;***************************************************************************** ; ; asninit is called to initialize the async support routines ; ; it MUST be called before any of the other asynch routines ; argument should be 0 for COM1 or 1 for COM2 ; ; syntax - asninit(comport) ; ;***************************************************************************** _asninit proc near cli ;disable interrupts push bp mov bp,sp mov ax,@AB[bp] ;get argument mov bx,ax ;get adapter selection value into bx cmp bx,1 ;test for invalid value jna asi2 ;ok, continue mov bx,0 ;invalid, assume 0 asi2: mov al,imlist[bx] ;get selected interrupt mask byte mov imbyte,al ;save it in imbyte add bx,bx ;convert to index into iolist mov ax,iolist[bx] ;get i/o adapter base address mov ioaddr,ax ;store into ioaddr mov ax,ivlist[bx] ;get interrupt vector address mov ivaddr,ax ;store into ivaddr mov cx,cs ;get current cs into cx mov dx,offset asnint ;get offset of interrupt routine mov bx,ivaddr ;get interrupt vector address mov ax,0 push ds mov ds,ax ;set ds to 0 mov [bx+2],cx ;set interrupt vector in low mem mov [bx],dx pop ds mov ax,offset dgroup:rbfbeg ;get offset of buffer mov rbhead,ax ;initialize buffer empty pointer mov rbtail,ax ;initialize buffer fill pointer IF XMITI mov ax,offset dgroup:xbfbeg ;get offset of buffer mov xbhead,ax ;initialize buffer empty pointer mov xbtail,ax ;initialize buffer fill pointer mov ax,BSIZE ;get buffer size mov xbcnt,ax ;initialize buffer room count ENDIF in al,PICMSK ;read 8259 interrupt mask and al,imbyte ;enable the async interrupt out PICMSK,al ;output the new mask IF XMITI mov al,00000011b ;interrupt mask for 8250 (rx & tx) ELSE mov al,00000001b ;interrupt mask for 8250 (rx only) ENDIF mov dx,ASIER ;interrupt enable register address add dx,ioaddr ;get adapter address out dx,al ;enable interrupts on 8250 mov al,00001011b ;rts,dtr,out2 bits in 8250 mcr mov dx,ASMCR ;8250 modem control register address add dx,ioaddr ;get adapter base address out dx,al ;set modem control register bits mov al,LCRBYTE ;set line control register mov dx,ASLCR ;lcr address add dx,ioaddr ;get adapter address out dx,al ;set lcr sti ;re-enable interrupts pop bp ret _asninit endp ;***************************************************************************** ; ; asnbaud is called to set the 8250 baud latch ; ; syntax - asynbaud(baudrate) ; ;***************************************************************************** _asnbaud proc near push bp mov bp,sp mov ax,@AB[bp] ;get argument to AX mov cx,ax ;baud rate (divisor) into cx mov ax,word ptr clock ;low order of dividend into ax mov dx,word ptr clock+2 ;hi order of dividend into dx div cx ;divide to get 8250 divisor word mov cx,ax ;get result into cx temporarily mov dx,ASLCR ;8250 Line control register address add dx,ioaddr ;add adapter base address in al,dx ;get current LCR mov bl,al ;...save in BL or al,10000000b ;turn Divisor Latch Enable bit on out dx,al ;...in LCR mov dx,ASDLL ;8250 Divisor Latch Low order address add dx,ioaddr ;add adapter base address mov al,cl ;get low order byte of divisor word out dx,al ;output to the Divisor Latch register mov dx,ASDLH ;8250 Divisor Latch Hi order address add dx,ioaddr ;add adapter base address mov al,ch ;get hi order byte of divisor word out dx,al ;output to the Divisor Latch register mov dx,ASLCR ;LCR address add dx,ioaddr ;add adapter base address mov al,bl ;old LCR contents out dx,al ;restore old LCR contents pop bp ret _asnbaud endp ;***************************************************************************** ; ; asnget is called to get a character from asynch receive buffer ; ; it returns the character or ; -1 if no character is available in the buffer ; ;***************************************************************************** _asnget proc near pushf ;save interrupt state cli ;disable interrupts mov bx,rbhead ;buffer empty pointer into bx mov ax,rbtail ;buffer fill pointer into ax cmp ax,bx ;see if data in circular buffer jz asngx ;no, return -1 to caller mov al,[bx] ;get character from buffer into al inc bx ;bump buffer empty pointer cmp bx,offset dgroup:rbfend ;test for end of buffer jnz asng1 ;no, continue mov bx,offset dgroup:rbfbeg ;yes, reset buffer empty pointer asng1: mov rbhead,bx ;update buffer empty pointer mov ah,0 ;make sure ax is a character POPFF ;restore interrupt state ret asngx: mov ax,0ffffh ;set ax to -1 to indicate no char POPFF ;restore interrupt state ret _asnget endp IF XMITI ;***************************************************************************** ; ; asnput is called to output a character to the asynch device ; ; syntax - asnput(char) ; ;***************************************************************************** _asnput proc near push bp mov bp,sp pushf ;save interrupt state asnp00: cli ;temporarily disable interrupts cmp xbcnt,BSIZE ;buffer empty? jne asnp0a ;no, continue mov dx,ASLSR ;8250 line status register address add dx,ioaddr ;add adapter base address in al,dx ;get line status byte test al,01000000b ;test for Transmit empty jz asnp0a ;no, store byte in buffer mov ax,@AB[bp] ;get argument in ax mov dx,ASTHR ;address of 8250 xmit hold register add dx,ioaddr ;add adapter base address out dx,al ;xmit the character POPFF ;restore interrupt state pop bp ret asnp0a: cmp xbcnt,0 ;room left in buffer? jne asnp01 ;yes, continue sti ;enable interrupts nop ;waste a little time jmp asnp00 ;and check again asnp01: mov bx,xbtail ;buffer fill pointer mov ax,@AB[bp] ;get argument in ax mov [bx],al ;store character in buffer inc bx ;bump pointer dec xbcnt ;and decrement room in buffer cmp bx,offset dgroup:xbfend ;test for end of buffer jb aspn1 ;no, continue mov bx,offset dgroup:xbfbeg ;offset of buffer start aspn1: mov xbtail,bx ;update buffer fill pointer POPFF ;restore interrupt state pop bp ret _asnput endp ELSE ;***************************************************************************** ; ; asnput is called to output a character to the asynch device ; ; syntax - asnput(char) ; ;***************************************************************************** _asnput proc near push bp mov bp,sp mov dx,ASLSR ;8250 line status register address add dx,ioaddr ;add adapter base address asnp0: in al,dx ;get line status byte test al,00100000b ;test for THRE jz asnp0 ;no, loop mov ax,@AB[bp] ;get argument in ax mov dx,ASTHR ;address of 8250 xmit hold register add dx,ioaddr ;add adapter base address out dx,al ;xmit the character pop bp ret _asnput endp ENDIF ;***************************************************************************** ; ; asnfls is called to flush the transmit data buffer ; (i.e. wait until all characters have been transmitted) ; ;***************************************************************************** _asnfls proc near IF XMITI asnf0: cmp xbcnt,BSIZE ;test for xmit buffer empty jnz asnf0 ;no, keep waiting ENDIF mov dx,ASLSR ;8250 line status register address add dx,ioaddr ;add adapter base address asnf1: in al,dx ;get line status byte test al,01000000b ;test for TSRE jz asnf1 ;no, loop ret _asnfls endp ;***************************************************************************** ; ; asnstat is called to obtain the asynch status bits ; ; the modem status bits are returned in high order byte ; the line status bits (error bits only) are returned in low order byte ; ;***************************************************************************** _asnstat proc near mov dx,ASMSR ;8250 modem status register address add dx,ioaddr ;add adapter base address in al,dx ;get modem status byte mov ah,al ;into ah dec dx ;address of 8250 line status register in al,dx ;get line status byte and al,00011110b ;strip everything but error bits ret _asnstat endp ;***************************************************************************** ; ; asnclr is called to flush the receive data buffer ; ;***************************************************************************** _asnclr proc near cli ;disable interrupts mov ax,offset dgroup:rbfbeg ;offset of buffer beginning mov rbhead,ax ;reset buffer empty pointer mov rbtail,ax ;reset buffer fill pointer sti ;re-enable interrupts ret _asnclr endp ;***************************************************************************** ; ; asnexit must be called to terminate the asynch support routines ; it disables the asynch interrupts which MUST be done ; before the calling program exits to DOS ; ; Failure to call this routine prior to returning back to DOS ; will leave the asynch interrupt vectors pointing into the ; DOS user program area, with probable disasterous results ; if a character comes in from the asynch line. ; ;***************************************************************************** _asnexit proc near cli in al,PICMSK ;get 8259 interrupt mask mov bl,imbyte ;get interrupt mask byte not bl ;invert it or al,bl ;turn off async interrupt out PICMSK,al ;output updated mask to 8259 mov al,0 ;turn off all 8250 interrupts mov dx,ASIER ;8250 interrupt mask register address add dx,ioaddr ;add adapter base address out dx,al ;output new mask mov dx,ASMCR ;8250 modem control register address add dx,ioaddr ;add adapter base address out dx,al ;turn off dtr,rts,out2 bits sti ret _asnexit endp page ;***************************************************************************** ; ; asnint is the asynch interrupt handler. it is NOT user callable ; ;***************************************************************************** assume cs:_TEXT,ds:DGROUP asnint proc far push ds ;asynchronous interrupt handler push dx ;save all registers push bx push ax mov ax,DGROUP mov ds,ax mov dx,ASIIR ;address of interrupt id register add dx,ioaddr ;add adapter base address in al,dx ;get interrupt status asi0: cmp al,0000100b ;test for receiver interrupt je asir ;yes, process receiver interrupt IF XMITI cmp al,0000010b ;test for transmitter empty je asit ;yes, process xmitter empty ENDIF jmp asix ;neither, ignore the interrupt ;***************************************************************************** ; ; received data available interrupt ; ;***************************************************************************** asir: mov dx,ASRBR ;address of receiver buffer register add dx,ioaddr ;add adapter base address in al,dx ;get data byte from 8250 rbr mov bx,rbtail ;buffer fill pointer mov [bx],al ;store character in buffer inc bx ;bump pointer cmp bx,offset dgroup:rbfend ;test for end of buffer jb asin1 ;no, continue mov bx,offset dgroup:rbfbeg ;offset of buffer start asin1: mov rbtail,bx ;update buffer fill pointer jmp asix ;exit from interrupt IF XMITI ;***************************************************************************** ; ; transmit buffer empty interrupt ; ;***************************************************************************** asit: mov bx,xbcnt ;get buffer room count cmp bx,BSIZE ;buffer empty? je asix ;yes, exit mov bx,xbhead ;get buffer head mov al,[bx] ;get character from buffer into al inc bx ;bump buffer empty pointer cmp bx,offset dgroup:xbfend ;test for end of buffer jnz asitg1 ;no, continue mov bx,offset dgroup:xbfbeg ;yes, reset buffer empty pointer asitg1: mov xbhead,bx ;update buffer empty pointer mov dx,ASTHR ;address of 8250 xmit hold register add dx,ioaddr ;add adapter base address out dx,al ;xmit the character inc xbcnt ;increment room count jmp asix ;exit from interrupt routine ENDIF ;***************************************************************************** ; ; exit interrupt routine ; ;***************************************************************************** asix: mov dx,ASIIR ;address of interrupt id register add dx,ioaddr ;add adapter base address in al,dx ;get interrupt status test al,00000001b ;test for another interrupt pending jz asi0 ;yes, process another one mov al,00100000b ;EOI for 8259 out PICCMD,al ;reset 8259 pop ax ;restore saved registers pop bx pop dx pop ds iret ;return from interrupt asnint endp _TEXT ENDS end