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Assembly Source File | 1990-02-11 | 18.0 KB | 571 lines

;-------------------------------------------------------------------- ; DUMBTERM ; Original author is CJ Dunford 09/12/83, modified by Jeff Firestone ; on 01/15/84. This program sets up the interrupt for COM1. It uses ; buffered communications. The program is based upon PC Tech Journal ; Jan '84, p144-186. ;--------------------------------------------------------------------- bufsize equ 4096 ;4K Buffer LF equ 0Ah CR equ 0Dh K_ESC equ 1Bh ; ------- BIOS calls RS232 equ 14h ;RS232 service kbd_io equ 16h ;Keyboard service ; ------- INS8250 registers THR equ 3F8h ;Trans holding register (write) RBR equ 3F8h ;Recieve buffer register (read) IER equ 3F9h ;Interrupt inable register LCR equ 3FBh ;Line control register ; Bit 7 of LCR is "DLAB". DLAB must ; be zero to access THR, RBR, IER. MCR equ 3FCh ;Modem control register LSR equ 3FDh ;Line status register MSR equ 3FEh ;Modem status register ; ------- Comm parameter definition ; Refer to IBM Tech Ref manual page A-20 ; See PROC INIT for usage. ; --------------------------------------- commparm record baud:3, parity:2, stopbits:1, wordbits:2 ; Buad rates B110 equ 000b B150 equ 001b B300 equ 010b B600 equ 011b B1200 equ 100b B2400 equ 101b B4800 equ 110b B9600 equ 111b ; Parity no_parity equ 00b odd_parity equ 01b even_parity equ 11b ; Stop bits stop1 equ 0 stop2 equ 1 ; Data bits data7 equ 10b data8 equ 11b ;***************************** ; MACROS ;***************************** @bioscall MACRO call_num, parm ;; Generates an 'INT call_num', with parm in AH IFNB <parm> mov ah,parm ENDIF int call_num ENDM @doscall MACRO function, parm ;; Generates a DOS function call with parm in AH IFNB <parm> mov al,parm ENDIF @bioscall 21h,function ENDM ;****************************** ; DATA & STACK SEGMENTS ;****************************** data segment para public 'data' ; ----- The string section sgreeting db '--- ONLINE -0--',cr,lf,'$' sgoodbye db cr,lf,'--- OFFLINE ---',cr,lf,'$' serr1 db '<R>$' ;RS232 receive error serr2 db '<S>$' ;RS232 send error serr3 db '<B>$' ;Receive buffer overflow error ; ----- Flags brcv_err db 0 ;Nonzero on RS232 receive error boverflow db 0 ;Nonzero on buffer overflow bdoneflag db 0 ;Nonzero after ESC from kbd ; ----- Receive data buffer and associated pointers ; >> Buffer is empty if head point4er = tail pointer wbufhead dw buffer ;Pointer to head of buffer wbuftail dw buffer ;Pointer to tail of buffer buffer db BUFSIZE dup (?) bufend equ $ data ends ; ----- Stack stack segment para stack 'stack' db 256 dup (?) stack ends ;* * * * * * * * * * * * * * * * * ; PROGRAM BODY ;* * * * * * * * * * * * * * * * * code segment para public 'code' assume cs:code, ds:data, ss:stack main proc far ; ------ Initialize push ds ;Set up long return to DOS sub ax,ax push ax call init ;Rest of initialization ; ------ Main program loop M100: call buffer_check ;Check RS232 buffer, display if char call kb_check ;Check kbd, Send to RS232. test bdoneflag,0FFh ;Non-zero if done jz M100 ;Loop till ESC received ; ------ ESC received. Clean up interrupt & exit call cleanup ret ;Return to DOS main endp ;* * * * * * * * * * * * * * * * * * * * ; PRIMARY BLOCKS ;* * * * * * * * * * * * * * * * * * * * ; ------ Init --------------------------------- ;Program initialization ; set up RS232 ; set up vector for RS232 interrupt (INT 0Ch) ; Enable IRQ4 ; Enable RS232 interrupt on data ready ; -------------------------------------------- init proc near ; ----- Initialize RS232 300,8,N,1 mov dx,0 mov al,commparm <B9600,even_Parity,stop1,data7> @bioscall RS232,0 ; ----- Set up INT '0C' for IRQ4 cli ;Interrupts off during setup push ds ;Save DS mov dx,offset ISR ;Point to RS232 ISR in DS:DX push cs pop ds @doscall 25h,0Ch ;Set vector intr for IRQ4 pop ds ;Restore DS ; ------ Enable IRQ4 on 8259 interrupt controller in al,21h ;Get current mask and al,11101111b ;Reset IRQ4 mask out 21h,al ;restore to IMR ; ------ Enable 8250 data ready interrupt mov dx,LCR ;DX <== LCR in al,dx ;reset DLAB for IER access and al,01111111b out dx,al mov dx,IER ;address IER mov al,00000001b ;Enable data-ready interrupt out dx,al ; ------ Enable OUT2 on 8250 mov dx,MCR ;Address MCR mov al,00001000b ;Enable OUT2 out dx,al sti ; ------ Display greeting & return mov ax,data ;Establish data seg address mov ds,ax mov dx,offset sgreeting ;Point to greeting call strdisp ;Display it ret init endp ; ------ Buffer Check ------------------ ; RS232 buffer check ; ; This block checks the received data buffer. ; It functions as follows: ; ; If the RS232 input buffer is not empty ; Get the first character ; Display the character ; Update buffer pointer ; If the RS232 receive error flag is nonzero ; Display an error indicator ; ; Entry: ; No requirement ; Exit ; AX, BX, DX destroyed ; -------------------------------------- buffer_check proc near ; ------ Check buffer status mov bx,wbufhead ;buffer head pointer cmp bx,wbuftail ;buffer empty if head = tail je BC100 ; ------ Something in buffer--get 1st char, fix pointers mov al,[bx] ;get the char call incptr ;Bump buffer head pointer mov wbufhead,bx ; ------ Display character received. Filter CR/LF cmp al,LF ;Is it a line feed je BC100 ;Skip display if yes call chdisp ;Display if no cmp al,CR jne BC100 mov al,LF call chdisp ; ------ Test RS232 receive status; display errors BC100: Test brcv_err,0FFh ;Flag nonzero if errors jz BC200 ;Jump if no errors mov dx,offset serr1 ;Point to error msg call strdisp mov brcv_err,0 ;Clear error flag ; ----- Test for buffer overflow; display errors BC200: test boverflow, 0FFh jz BC300 mov boverflow,0 ;Clear the flag mov dx,offset serr3 ;Point to error msg call strdisp BC300: ret buffer_check endp ; ----- KB_CHECK ----------------------------------- ; Check the keyboard. Functions as follows ; ; Check the keyboard status ; If a characteris available ; If the character is ESC ; set the done flag ; ELSE ; send it to RS232 and watch for errors ; ; This routine does not echo the characters to the display. ; ; Entry: ; No requirement ; Exit ; AX, DX destroyed ; -------------------------------------- kb_check proc near ; ----- Poll keyboard, check chars received call kb_poll ;Poll the keyboard jz KBC900 ;Kbd clear, exit cmp al,K_ESC ;Escape? jne KBC100 mov bdoneflag,0FFh ;Yes, set terminate flag jmp short KBC900 ; ----- Send the received char, watch for errors KBC100: Call RS232_out ;Send it test ah,80h ;Time out? jz KBC900 mov dx,offset serr2 ;Point to error msg call strdisp ; and display KBC900: ret kb_check endp ; ----- ISR ------------------------------------------------------ ; This is the RS232 interrupt service routine. It is entered ; whenever the RS232 port interrupts on a 'data ready' ; condition. The routine simply reads the data from the asynch ; chip and stuffs it in the buffer. Note that the process of reading ; the received data register in the 8250 clears IRQ4. However, the ; 8259 must be told specifically that the interrupt service is complete. ; ; This replaces the function 2 of BIOS interrupt 14h (receive a character ; over the comm line). Since it cannot return errors in a register, it ; puts the error marker in memory at 'brcv_err'. The error flag is ; sticky -- a successful read will not clear a prior error indication. ; This allows the program mainline to examine the error status at its ; leisure. Error bits are the same as in RS232OUT, above, except that ; ONLY the error bits are set, and bit 7 is not used (always 0). In ; other words, brcv_err is nonzero only on an error. Timeout errors ; are not possible here. ; ; The ISR will set the overflow flag if the buffer should overflow. ; This shouldn't happen. ; -------------------------------------------------------------------- ISR proc near sti ;Allow other interrupts push ax ;Save all regs used push bx push dx push si push ds ; ---- Establish data addressability mov ax,data mov ds,ax ; ---- Get error bits mov dx,LSR ;Save address of RS232 in al,dx ;Get status and al,00011110b ;Mask non-error bits jz ISR010 ;Skip error set if OK mov brcv_err,al ;Set error indicator ; ---- Get incoming character and buffer it ISR010: mov dx,RBR ;Receive buffer in al,dx ;Get input buffer mov bx,wbuftail ;Buffer input pointer mov si,bx ;Set pointer before increment call incptr ;Bump input pointer cmp bx,wbufhead ;Overflow if head = tail je ISR020 ;Overflow mov [si],al ;No overflow, save char in buf mov wbuftail,bx ;And new input pointer jmp short ISR999 ISR020: mov boverflow, 0FFh ;Set overflow flag ; ---- Signal end of interrupt to 8259 ISR999: cli mov al,20h ;Non-specific EOI out 20h,al ;Send it ; ---- Restore regs & return. IRET reenables interrupts pop ds pop si pop dx pop bx pop ax iret ISR endp ; ---- CLEANUP -------------------- ; End of program housekeeping ; -- Disable IRQ4 ; -- Disable 8250 interrupts ; -- Disable OUT2 ; -- Display offline message ; --------------------------------- cleanup proc near ; ---- Disable IRQ4 on 8259 cli in al,21h ;IMR or al,00010000b ;Mask bit 4 -- IRQ4 out 21h,al ; ---- Disable 8250 data ready interrupt mov dx, LCR ;DX <=== LCR in al,dx ;Reset DLAB for IER access and al,01111111b out dx,al mov dx,IER ;Address IER mov al,0 ;Disable all 8250 interrupts out dx,al ; ---- Disable OUT2 on 8250 mov dx,MCR ;Address MCR mov al,0 ;Disable OUT2 out dx,al sti ; ---- Display bye-bye mov dx,offset sgoodbye call strdisp cleanup endp ; * * * * * * * * * * * * * * ; I/O & General Subroutines ; * * * * * * * * * * * * * * ; ---- KB_POLL ------------------------------ ; Set/reset Z flag on keyboard buffer status. ; ; Entry: ; No requirements ; Exit: ; Z = 1 if nothing available ; Z = 0 if char available from kbd ; IF Z = 0 ; AL = char ; AH = scan code ; Other regs preserved ; --------------------------------------------- kb_poll proc near @bioscall kbd_io,1 ;Poll KB. Sets Z flag if KB bfr empty jz KB999 ;Nothing there pushf ;Save flag status @bioscall kbd_io,0 ;Something there; get it popf KB999: ret kb_poll endp ; -- RS232_OUT ---------------------------------------- ; RS232 output routine ; ; This routine sends one character to the RS232 port. ; It replaces function 1 of BIOS int 14K. This is ; necessary because BIOS will disable the RS232 ; interrupt (by disabling OUT2) every time it is ; called. ; ; Entry: ; AL = character to be transmitted ; Exit: ; AH = send status ; Bit 7 = 1 if RS232 timeout occurred ; If bit 7 = 0 ; bit 6: trans shift register empty ; bit 5: trans holding register empty ; bit 4: break detect ; bit 3: framing error ; bit 2: parity error ; bit 1: overrun error ; bit 0: data ready ; Other regs preserved. ; ------------------------------------------------------- RS232_out proc near push bx ;Save regs used push cs push dx ; ----- Set up RS232 mov bl,al ;Save char to bl temporarily mov dx,MCR ;Modem Control Register mov al,00001011b ; OUT2, DTR, RTS out dx,al sub cx,cx ;Initialize timeout count mov dx,MSR ;Modem Status Register ; ----- Wait for DSR RS100: in al,dx test al,20h ;Data set ready? jnz RS150 ;Yes loop RS100 ;No, retry till timeout mov ah,80h ;Set timeout jmp short RSXIT ;and quit ; ----- Wait for CTS RS150: sub cx,cx ;Another timeout count RS200: in al,dx test al,10h ;Clear to send? jnz RS250 ;Yes loop RS200 ;No, loop till timeout mov ah,80h ;TImeout,set flag jmp short RSXIT ;And quit ; ----- Wait for THRE RS250: mov dx,LSR ;Line Status Register sub cx,cx ;Yes another timeout count RS300: in al,dx ;LSR status test al,20h ;Transmit holding reg empty? jnz RS350 ;Yes loop RS300 ;No, loop till timeout mov ah,80h ;Timeout, set flag jmp short RSXIT ; ------ Get line status, send char RS350: mov ah,al ;Get line status for return and ah,01111111b ;Mask out bit 7 mov al,bl ;Restore char to AL mov dx,THR ;Transmit holding register out dx,al ;Output it to RS232 RSXIT: pop dx pop cx pop bx ret RS232_out endp ; ---- CHDISP ---------------------------------- ; Display the character in AL on the CRT ; Entry: ; AL = char ; Exit: ; All regs restored ; ---------------------------------------------- chdisp proc near push ax push dx mov dl,al @doscall 2 pop dx pop ax ret chdisp endp ; ---- STRDISP ---------------------------- ; Display the string at DS:DX on the CRT ; Entry: ; DS:DX ==> string ; Exit: ; All regs restored ; ----------------------------------------- strdisp proc near push ax @doscall 9 pop ax ret strdisp endp ; ----- INCPTR ------------------------------ ; Increments the buffer pointer in reg BX. ; If the pointer goes beyond the end of the ; buffer, wrap around to start. ; ; Entry: ; BX = buffer pointer ; Exit ; BX = advanced buffer pointer ; Other regs restored ; -------------------------------------------- incptr proc near inc bx ; Bump pointer cmp bx,offset bufend ; Past end? jne IP100 ; Jump if not mov bx,offset buffer ; Else point to start IP100: ret incptr endp code ends end main