Microsoft Programmer's Library 1.3

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Assembly Source File | 1988-10-01 | 18.8 KB | 571 lines

title TALK --- Simple terminal emulator page 55,132 .lfcond ;list false conditionals too ; ; TALK.ASM --- Simple IBM PC terminal emulator ; ; Copyright (c) 1988 Ray Duncan ; ; Build: MASM TALK; ; LINK TALK; ; ; Usage: TALK ; stdin equ 0 ; standard input handle stdout equ 1 ; standard output handle stderr equ 2 ; standard error handle cr equ 0dh ; ASCII carriage return lf equ 0ah ; ASCII line feed bsp equ 08h ; ASCII backspace escape equ 1bh ; ASCII escape code dattr equ 07h ; display attribute to use ; while in emulation mode bufsiz equ 4096 ; size of serial port buffer echo equ 0 ; 0=full-duplex, -1=half-duplex true equ -1 false equ 0 com1 equ true ; Use COM1 if nonzero com2 equ not com1 ; Use COM2 if nonzero pic_mask equ 21h ; 8259 int. mask port pic_eoi equ 20h ; 8259 EOI port if com1 com_data equ 03f8h ; port assignments for COM1 com_ier equ 03f9h com_mcr equ 03fch com_sts equ 03fdh com_int equ 0ch ; COM1 interrupt number int_mask equ 10h ; IRQ4 mask for 8259 endif if com2 com_data equ 02f8h ; port assignments for COM2 com_ier equ 02f9h com_mcr equ 02fch com_sts equ 02fdh com_int equ 0bh ; COM2 interrupt number int_mask equ 08h ; IRQ3 mask for 8259 endif _TEXT segment word public 'CODE' assume cs:_TEXT,ds:_DATA,es:_DATA,ss:STACK talk proc far ; entry point from MS-DOS mov ax,_DATA ; make data segment addressable mov ds,ax mov es,ax ; initialize display for ; terminal emulator mode... mov ah,15 ; get display width and int 10h ; current display mode dec ah ; save display width for use mov columns,ah ; by the screen clear routine cmp al,7 ; enforce text display mode je talk2 ; mode 7 ok, proceed cmp al,3 jbe talk2 ; modes 0-3 ok,proceed mov dx,offset msg1 mov cx,msg1_len jmp talk6 ; print error message and exit talk2: mov bh,dattr ; clear screen and home cursor call cls call asc_enb ; capture serial port interrupt ; vector and enable interrupts mov dx,offset msg2 ; display message mov cx,msg2_len ; 'Terminal emulator running' mov bx,stdout ; BX = standard output handle mov ah,40h ; Fxn 40H = write file or device int 21h ; transfer to MS-DOS talk3: call pc_stat ; keyboard character waiting? jz talk4 ; nothing waiting, jump call pc_in ; read keyboard character cmp al,0 ; is it a function key? jne talk32 ; not function key, jump call pc_in ; function key, discard 2nd ; character of sequence jmp talk5 ; then terminate program talk32: ; keyboard character received if echo push ax ; if half-duplex, echo call pc_out ; character to PC display pop ax endif call com_out ; write char. to serial port talk4: call com_stat ; serial port character waiting? jz talk3 ; nothing waiting, jump call com_in ; read serial port character cmp al,20h ; is it control code? jae talk45 ; jump if not call ctrl_code ; control code, process it jmp talk3 ; check keyboard again talk45: ; non-control char. received, call pc_out ; write it to PC display jmp talk4 ; see if any more waiting talk5: ; function key detected, ; prepare to terminate... mov bh,07h ; clear screen and home cursor call cls mov dx,offset msg3 ; display farewell message mov cx,msg3_len talk6: push dx ; save message address push cx ; and message length call asc_dsb ; disable serial port interrupts ; and release interrupt vector pop cx ; restore message length pop dx ; and address mov bx,stdout ; handle for standard output mov ah,40h ; Fxn 40H = write device int 21h ; transfer to MS-DOS mov ax,4c00h ; terminate program with int 21h ; return code = 0 talk endp com_stat proc near ; Check asynch status, returns ; Z=false if character ready ; Z=true if nothing waiting push ax mov ax,asc_in ; compare ring buffer pointers cmp ax,asc_out pop ax ret ; return to caller com_stat endp com_in proc near ; get character from serial ; port buffer, returns ; new character in AL push bx ; save register BX com_in1: ; if no char waiting, wait mov bx,asc_out ; until one is received cmp bx,asc_in je com_in1 ; jump, nothing waiting mov al,[bx+asc_buf] ; character is ready, ; extract it from buffer inc bx ; update buffer pointer cmp bx,bufsiz jne com_in2 xor bx,bx ; reset pointer if wrapped com_in2: mov asc_out,bx ; store updated pointer pop bx ; restore register BX ret ; and return to caller com_in endp com_out proc near ; write character in AL ; to serial port push dx ; save register DX push ax ; save character to send mov dx,com_sts ; DX = status port address com_out1: ; check if transmit buffer in al,dx ; is empty (TBE bit = set) and al,20h jz com_out1 ; no, must wait pop ax ; get character to send mov dx,com_data ; DX = data port address out dx,al ; transmit the character pop dx ; restore register DX ret ; and return to caller com_out endp pc_stat proc near ; read keyboard status, returns ; Z=false if character ready ; Z=true if nothing waiting. ; register DX destroyed. mov al,in_flag ; if character already or al,al ; waiting, return status jnz pc_stat1 mov ah,6 ; otherwise call MS-DOS to mov dl,0ffh ; determine keyboard status int 21h jz pc_stat1 ; jump if no key ready mov in_char,al ; got key, save it for mov in_flag,0ffh ; "pc_in" routine pc_stat1: ; return to caller with ret ; Z flag set appropriately pc_stat endp pc_in proc near ; read keyboard character, ; return it in AL ; DX may be destroyed. mov al,in_flag ; key already waiting? or al,al jnz pc_in1 ; yes,return it to caller call pc_stat ; try and read a character jmp pc_in pc_in1: mov in_flag,0 ; clear char. waiting flag mov al,in_char ; and return AL = character ret pc_in endp pc_out proc near ; write character in AL ; to the PC's display. mov ah,0eh ; ROM BIOS Fxn 0EH = ; "teletype output" push bx ; save register BX xor bx,bx ; assume page 0 int 10h ; transfer to ROM BIOS pop bx ; restore register BX ret ; and return to caller pc_out endp cls proc near ; clear display using ; char. attribute in BH ; registers AX, CX, ; and DX destroyed. mov dl,columns ; set DL,DH = X,Y of mov dh,24 ; lower right corner mov cx,0 ; set CL,CH=X,Y of ; upper left corner mov ax,600h ; ROM BIOS Fxn 06H = ; "scroll or initialize ; window" int 10h ; transfer to ROM BIOS call home ; set cursor at (0,0) ret ; and return to caller cls endp clreol proc near ; clear from cursor to end ; of line using attribute ; in BH. Register AX, CX, ; and DX destroyed. call getxy ; get current cursor pos'n mov cx,dx ; current position = "upper ; left corner" of window mov dl,columns ; "lower right corner" X is ; max columns, Y is same ; as upper left corner mov ax,600h ; ROM BIOS Fxn 06H = ; "scroll or initialize ; window" int 10h ; transfer to ROM BIOS ret ; return to caller clreol endp home proc near ; put cursor at home position mov dx,0 ; set (X,Y) = (0,0) call gotoxy ; position the cursor ret ; return to caller home endp gotoxy proc near ; position the cursor ; call with DL=X, DH=Y push bx ; save registers push ax mov bh,0 ; assume page 0 mov ah,2 ; ROM BIOS Fxn 02H = ; set cursor position int 10h ; transfer to ROM BIOS pop ax ; restore registers pop bx ret ; and return to caller gotoxy endp getxy proc near ; get cursor position, ; Returns DL=X, DH=Y push ax ; save registers push bx push cx mov ah,3 ; ROM BIOS Fxn 03H = ; get cursor position mov bh,0 ; assume page 0 int 10h ; transfer to ROM BIOS pop cx ; restore registers pop bx pop ax ret ; and return to caller getxy endp ctrl_code proc near ; process control code ; call with AL=char cmp al,cr ; if carriage return je ctrl8 ; just send it cmp al,lf ; if line feed je ctrl8 ; just send it cmp al,bsp ; if backspace je ctrl8 ; just send it cmp al,26 ; is it cls control code? jne ctrl7 ; no, jump mov bh,dattr ; cls control code, clear call cls ; screen and home cursor jmp ctrl9 ctrl7: cmp al,escape ; is it Escape character? jne ctrl9 ; no, throw it away call esc_seq ; yes, emulate CRT terminal jmp ctrl9 ctrl8: call pc_out ; send CR, LF, or backspace ; to the display ctrl9: ret ; return to caller ctrl_code endp esc_seq proc near ; decode Televideo 950 escape ; sequence for screen control call com_in ; get next character cmp al,84 ; is it clear to end of line? jne esc_seq1 ; no, jump mov bh,dattr ; yes, clear to end of line call clreol jmp esc_seq2 ; then exit esc_seq1: cmp al,61 ; is it cursor positioning? jne esc_seq2 ; no jump call com_in ; yes, get Y parameter sub al,33 ; and remove offset mov dh,al call com_in ; get X parameter sub al,33 ; and remove offset mov dl,al call gotoxy ; position the cursor esc_seq2: ; return to caller ret esc_seq endp asc_enb proc near ; capture serial port interrupt ; vector and enable interrupt ; save address of previous ; interrupt handler... mov ax,3500h+com_int ; Fxn 35H = get vector int 21h ; transfer to MS-DOS mov word ptr oldvec+2,es mov word ptr oldvec,bx ; now install our handler... push ds ; save our data segment mov ax,cs ; set DS:DX = address mov ds,ax ; of our interrupt handler mov dx,offset asc_int mov ax,2500h+com_int ; Fxn 25H = set vector int 21h ; transfer to MS-DOS pop ds ; restore data segment mov dx,com_mcr ; set modem control register mov al,0bh ; DTR and OUT2 bits out dx,al mov dx,com_ier ; set interrupt enable mov al,1 ; register on serial out dx,al ; port controller in al,pic_mask ; read current 8259 mask and al,not int_mask ; set mask for COM port out pic_mask,al ; write new 8259 mask ret ; back to caller asc_enb endp asc_dsb proc near ; disable interrupt and ; release interrupt vector in al,pic_mask ; read current 8259 mask or al,int_mask ; reset mask for COM port out pic_mask,al ; write new 8259 mask push ds ; save our data segment lds dx,oldvec ; load address of ; previous interrupt handler mov ax,2500h+com_int ; Fxn 25H = set vector int 21h ; transfer to MS-DOS pop ds ; restore data segment ret ; back to caller asc_dsb endp asc_int proc far ; interrupt service routine ; for serial port sti ; turn interrupts back on push ax ; save registers push bx push dx push ds mov ax,_DATA ; make our data segment mov ds,ax ; addressable cli ; clear interrupts for ; pointer manipulation mov dx,com_data ; DX = data port address in al,dx ; read this character mov bx,asc_in ; get buffer pointer mov [asc_buf+bx],al ; store this character inc bx ; bump pointer cmp bx,bufsiz ; time for wrap? jne asc_int1 ; no, jump xor bx,bx ; yes,reset pointer asc_int1: ; store updated pointer mov asc_in,bx sti ; turn interrupts back on mov al,20h ; send EOI to 8259 out pic_eoi,al pop ds ; restore all registers pop dx pop bx pop ax iret ; return from interrupt asc_int endp _TEXT ends _DATA segment word public 'DATA' in_char db 0 ; PC keyboard input char. in_flag db 0 ; <>0 if char waiting columns db 0 ; highest numbered column in ; current display mode (39 or 79) msg1 db cr,lf db 'Display must be text mode.' db cr,lf msg1_len equ $-msg1 msg2 db 'Terminal emulator running...' db cr,lf msg2_len equ $-msg2 msg3 db 'Exit from terminal emulator.' db cr,lf msg3_len equ $-msg3 oldvec dd 0 ; original contents of serial ; port interrupt vector asc_in dw 0 ; input pointer to ring buffer asc_out dw 0 ; output pointer to ring buffer asc_buf db bufsiz dup (?) ; communications buffer _DATA ends STACK segment para stack 'STACK' db 128 dup (?) STACK ends end talk ; defines entry point