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Assembly Source File | 1986-06-19 | 11.9 KB | 446 lines

name talk page 55,132 .lfcond ;list false conditionals too title 'TALK --- IBM PC terminal emulator' ; ; TALK.ASM --- a simple terminal emulator for the IBM PC ; ; Copyright (c) 1983, 1984, 1985 Ray Duncan ; ; To assemble, link, and convert this program into ; a COM file, follow these steps: ; ; C>MASM TALK; ; C>LINK TALK; ; C>EXE2BIN TALK.EXE TALK.COM ; C>DEL TALK.EXE ; ; Ignore the message "Warning: no stack segment" from the Linker. cr equ 0dh ;ASCII carriage return lf equ 0ah ;ASCII line feed bsp equ 08h ;ASCII backspace esc equ 1bh ;ASCII escape code dattr equ 07h ;display attribute to use ;while in emulation mode echo equ 0 ;0=full-duplex, -1=half-duplex comm_port equ 0 ;set =0 for COM1, <>0 for COM2 pic_mask equ 21h ;port address, 8259 mask register pic_eoi equ 20h ;port address, 8259 EOI instr. if comm_port ;define physical port assignments comm_data equ 02f8h ;for COM2 comm_ier equ 02f9h comm_mcr equ 02fch comm_stat equ 02fdh com_int equ 0bh int_mask equ 08h ;Mask for 8529, COM2 is IRQ3 else comm_data equ 03f8h ;port assignments for COM1 comm_ier equ 03f9h comm_mcr equ 03fch comm_stat equ 03fdh com_int equ 0ch int_mask equ 10h ;Mask for 8259, COM1 is IRQ4 endif page cseg segment para public 'CODE' org 100h assume cs:cseg,ds:cseg,es:cseg,ss:cseg ;COM file... talk proc far ;entry point from PC-DOS ;initialize display for ;terminal emulator mode mov ah,15 ;determine display width int 10h ;using get mode function of ROM dec ah ;BIOS video driver, save it for use mov columns,ah ;by the screen clear routine. cmp al,7 ;make sure display is text mode. je talk2 ;mode 7 ok, proceed cmp al,3 jbe talk2 ;modes 0-3 ok,proceed mov dx,offset msg1 jmp talk6 ;print error message and exit talk2: mov bh,dattr ;now clear screen with special call cls ;attribute if needed, home cursor call asc_enb ;set up communications interrupt ;service routine and enable int. talk3: call pc_stat ;check character waiting ;from the IBM PC keyboard jz talk4 ;nothing waiting, jump call pc_in ;read char. from PC keyboard cmp al,0 ;is it a function key? jne talk32 ;not function key, jump call pc_in ;read and discard the 2nd char ;of function key sequence jmp talk5 ;then exit the terminal emulator talk32: ;character received from PC keyboard if echo push ax ;if running half-duplex, echo call pc_out ;the character to the PC display pop ax endif call com_out ;write char. to the comm port talk4: call com_stat ;check if character waiting ;from the comm port jz talk3 ;no, loop call com_in ;read char. from comm port cmp al,20h ;is it control code? jae talk45 ;no call ctrl_code ;yes,process it jmp talk3 ;check local keyboard talk45: call pc_out ;write it to the PC display jmp talk4 ;see if any more waiting talk5: ;ESC key detected, prepare ;to exit the terminal emulator. mov bh,07h ;clear screen & home cursor call cls ;with "normal" video attribute mov dx,offset msg2 ;print farewell message talk6: push dx ;save message addr call asc_dsb ;disable controller and pop dx ;release interrupt vector mov ah,9 ;print message int 21h mov ax,4c00h ;exit with ret code=0 int 21h talk endp com_stat proc near ;Check asynch status, returns ;Z=false if character ready ;Z=true if nothing waiting push dx mov dx,asc_in ;compare ring buffer pointers cmp dx,asc_out pop dx ret com_stat endp com_in proc near ;get a char from asynch line push bx ;returns char in AL com_in1: ;if no char waiting, loop mov bx,asc_out ;until one is received. cmp bx,asc_in je com_in1 mov al,[bx+asc_buf] inc bx cmp bx,asc_buf_len jne com_in2 xor bx,bx ;reset ring pointer com_in2: mov asc_out,bx ;store updated pointer pop bx ret com_in endp com_out proc near ;write character in AL to COM port push dx push ax ;save char mov dx,comm_stat ;check TBE status com_out1: in al,dx and al,20h jz com_out1 pop ax ;write char mov dx,comm_data out dx,al pop dx ret com_out endp pc_stat proc near ;read status for the IBM ;PC's keyboard, returns ;Z=false if character ready ;Z=true if nothing waiting. ;register DX destroyed. mov al,in_flag ;if a character is already or al,al ;waiting,just return status jnz pc_stat1 mov ah,6 ;otherwise call PC-DOS to mov dl,0ffh ;determine status int 21h jz pc_stat1 ;jump,nothing ready ;got a char, save it for ;"pc_in" routine. mov in_char,al mov in_flag,0ffh pc_stat1: ;return to caller with ret ;Z flag set appropriately pc_stat endp pc_in proc near ;read a character from the ;IBM PC's keyboard, return ;it in AL. DX may be destroyed. mov al,in_flag or al,al ;any character waiting? 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 ;exit with AL=char ret pc_in endp pc_out proc near ;write the character in AL ;to the PC's display. mov ah,0eh ;use ROM BIOS TTY output fxn push bx ;save register xor bx,bx ;assume page 0 int 10h ;call ROM BIOS video driver pop bx ;restore register ret pc_out endp cls proc near ;clear the display and set ;it to the attribute in BH. ;registers AX, CX, DX destroyed. mov dl,columns mov dh,24 ;DL,DH=X,Y of lower right ;corner of "window". mov cx,0 ;CL,CH=X,Y of upper left ;corner of "window". mov ax,600h ;AH=6 for "scroll or initialize ;window" function, AL=0 for ;number of lines to scroll. int 10h ;call ROM BIOS video driver. call home ;set cursor at (0,0) ret cls endp clreol proc near ;clear from cursor to end of line ;using the attribute in BH. ;registers AX, CX, DX destroyed. call getxy mov cx,dx ;current position = "upper left" ;corner of window mov dl,columns ;for "lower right", X is max columns, ; Y is the same mov ax,600h ;AH=6 for "scroll or initialize ;window" function, AL=0 for ;number of lines to scroll. int 10h ;call ROM BIOS video driver. ret clreol endp home proc near ;home cursor (set X,Y=0,0) mov dx,0 call gotoxy ret home endp gotoxy proc near ;position the cursor, call ;with (DL,DH)=(X,Y) push bx ;save registers push ax mov bh,0 ;assume page 0 mov ah,2 int 10h ;call ROM BIOS video driver pop ax ;restore registers pop bx ret gotoxy endp getxy proc near ;get the current cursor position, ;returns (DL,DH)=(X,Y) push ax ;save registers push bx push cx mov ah,3 mov bh,0 ;assume page 0 int 10h ;call ROM BIOS video driver pop cx ;restore registers pop bx pop ax ret getxy endp ctrl_code proc near ;process a control code character ;call with AL=char cmp al,cr ;if line feed or carriage je ctrl8 ;return, just send it cmp al,lf je ctrl8 cmp al,bsp ;or if backspace, just send it je ctrl8 cmp al,26 ;is it clearscreen jne ctrl7 ;no,jump mov bh,dattr call cls ;clear screen and home cursor ret ctrl7: cmp al,esc ;is it escape char? jne ctrl9 ;no,throw it away call esc_seq ;yes,emulate CRT terminal ret ctrl8: call pc_out ;send CR or LF to display ctrl9: ret ;and exit ctrl_code endp esc_seq proc near ;decode Televideo 950 escape ;sequence to control the screen call com_in cmp al,84 ;clear to end of line jne esc_seq1 mov bh,dattr call clreol ret esc_seq1: cmp al,61 ;cursor positioning jne esc_seq2 call com_in ;get Y sub al,33 ;remove offset mov dh,al call com_in ;get X sub al,33 ;remove offset mov dl,al call gotoxy ;set cursor esc_seq2: ret esc_seq endp asc_enb proc near ;set up communications interrupt ;vector, and enable interrupt mov ah,35h ;get current address of asynch mov al,com_int ;port's interrupt handler int 21h ;ES:BX = addr mov intc_seg,es ;save segment mov intc_offs,bx ;save offset mov dx,offset asc_int mov ah,25h ;set address of new handler mov al,com_int int 21h mov dx,comm_mcr ;modem controller DTR & OUT2 mov al,0bh out dx,al mov dx,comm_ier ;interrupt enable register mov al,1 ;on asynch controller out dx,al in al,pic_mask ;read current 8259 int. mask and al,not int_mask ;reset mask for this COM port out pic_mask,al ;write back 8259 int. mask ret asc_enb endp asc_dsb proc near ;disable interrupt and release ;service vector ;vector, and enable interrupt in al,pic_mask ;read current 8259 int. mask or al,int_mask ;set mask for this COM port out pic_mask,al ;write int. mask back to 8259 push ds mov dx,intc_offs ;saved offset mov ds,intc_seg ;saved segment mov ah,25h ;restore address of original mov al,com_int ;com port interrupt handler int 21h pop ds ret asc_dsb endp asc_int proc far ;interrupt service routine ;for asynch controller sti ;turn interrupts back on push ax ;save all necessary registers push bx push dx push ds mov ax,cs mov ds,ax mov dx,comm_data in al,dx ;read this character cli ;clear interrupts for ;pointer manipulation mov bx,asc_in ;get buffer pointer mov [asc_buf+bx],al ;store this character inc bx ;bump pointer cmp bx,asc_buf_len ;time for wrap? jne asc_int1 ;no,jump xor bx,bx ;yes,reset pointer asc_int1: mov asc_in,bx ;store back updated pointer 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 ;and exit handler asc_int endp 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,'Display must be text mode.' db cr,lf,'$' msg2 db cr,lf,lf,'Exit from terminal emulator.' db cr,lf,'$' intc_offs dw 0 ;original contents of Int 0CH intc_seg dw 0 ;service vector asc_in dw 0 ;input pointer to ring buffer asc_out dw 0 ;output pointer to ring buffer asc_buf_len equ 16384 asc_buf equ this byte cseg ends end talk