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Assembly Source File | 1987-08-07 | 14.4 KB | 272 lines

; Source code for TSR, by John J. Newlin, Page 28, Volume 5.5, ; Programmer's Journal ; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;RAM resident KERNEL driver for main program in expanded memory ;Copyright 1987 by John J. Newlin, 4060-228 Rosenda Court, San ;Diego, CA 92122 ;All rights reserved ;Assemble with MASM, link with LINK, convert to .COM with EXE2BIN ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;Equates referencing offset addresses in the main program. Addresses ;derived from Turbo Pascal main program - see article text. activate equ 2D9FH demo_main equ 2DA6H emm_handle equ 2DAAH loaded_in_emm equ 2DA8H code segment assume cs:code org 100h begin: jmp initialize ;jump directly to initialization code demo LABEL DWORD ;label for far call to main prog demo_ofs dw 0 ;offset of main prog handler demo_seg dw 0 ;segment of main prog i16 LABEL DWORD ;label for far call/jump to int 16h i16_ofs dw 0 ;offset of original int 16h i16_seg dw 0 ;segment of original int 16h save_ss dw 0 ;save caller's SS reg save_sp dw 0 ;save caller's SP reg save_ax dw 0 ;save caller's AX reg hotkey db 0 ;hotkey value active db 0 ;active flag handle dw 0 ;EMM handle local_stack dw 20 dup(0) ;local stack area stkptr dw 0 ;local SP save_map: push ax push dx mov dx,cs:handle ;DX gets our handle mov ah,47h ;save mapping context int 67h ;call EMM pop dx pop ax ret ; restore_map: push ax push dx mov dx,cs:handle ;DX gets handle mov ah,48h ;to restore mapping context int 67h ;call EMM pop dx pop ax ret map_memory: push ax push bx push cx push dx mov cx,4 ;will map 4 pages do_again: mov dx,cs:handle ;DX gets handle mov bx,cx ;BX gets logical page mov al,cl ;AL gets physical page dec bx ;decrement logical page dec al ;decrement physical page mov ah,44h ;set up for EMM call int 67h ;call EMM loop do_again ;do again (3,2,1,0) pop ax pop bx pop cx pop dx ret ; run_demo: call save_map ;save mapping context call map_memory ;map our pages in mov cs:active,1 ;set active flag mov cs:save_ax,ax ;save AX reg cli ;turn off interrupts mov cs:save_ss,ss ;save caller's SS reg mov cs:save_sp,sp ;save caller's SP reg mov ax,cs ;get our CS mov ss,ax ;put in SS mov ax,offset cs:stkptr ;get offset of local stack mov sp,ax ;put in SP sub sp,2 ;decrement SP sti ;enable interrupts push ax ;save push bx ; caller's push cx ; regs push dx ; on push di ; our push si ; local push bp ; stack push es ; call cs:[demo] ;call our main prog pop es ;restore pop bp ; caller's pop si ; regs pop di ; from pop dx ; our pop cx ; local pop bx ; stack pop ax ; cli ;turn off interrupts mov ax,cs:save_ss ;get caller's SS reg mov ss,ax ;put in SS mov sp,cs:save_sp ;restore caller's SP mov ax,cs:save_ax ;restore caller's AX sti ;enable interrupts mov cs:active,0 ;reset active flag call restore_map ;restore mapping context ret ;return int16 proc far ;use far attr for returns cmp ah,98h ;regular int 16 request? jb keys16 ;yes n00: cmp ah,9Fh ;request to remove? jne l1 ;no mov ax,cs:demo_seg ;yes, prepare to remove mov es,ax ;ES gets frame segment mov ah,45h ;prepare to release EM mov dx,cs:handle ;load handle in DX int 67h ;call EMM to release cli ;turn of interrupts push ds ;save DS mov ax,cs:i16_seg ;get orginal int 16h seg mov ds,ax ;put in DS mov dx,cs:i16_ofs ;DX = original int 16h ofs mov ax,2516h ;set up to re-install int 21h ;call DOS to do it pop ds ;restore ds mov bx,2Ch ;2Ch in PSP has segment mov ax,cs:[bx] ;get mem block segment mov es,ax ;put in ES for DOS mov ah,49h ;set up to release int 21h ;call DOS to release mov ax,cs ;our segment mov es,ax ;put in ES for DOS mov ah,49h ;set up to release int 21h ;call DOS to release sti ;enable interrupts mov ah,4Ch ;set up to teminate int 21h ;call DOS to terminate l1: cmp ah,9Bh ;requ for presence flag? jne keys16 ;no mov ax,0ABCDh ;indicator in AX iret ;return to caller no_action16: jmp cs:[i16] ;jmp to original int 16h keys16: cmp cs:active,1 ;is demo active? je no_action16 ;yes - depart cmp ah,1 ;buffer status req? ja no_action16 ;no - depart je checkchar ;yes - process getchar: mov ah,0 ;set up to get a char pushf ;to fake int call call cs:[i16] ;call original int 16h cmp al,0 ;alt key pressed? jne exit0 ;no - depart cmp ah,cs:hotkey ;our hot key? je action1 ;yes - process exit0: iret ;no - return to caller action1: call run_demo ;call our main prog jmp getchar ;go check key buffer checkchar: mov ah,1 ;set up to check buffer pushf ;to fake int call call cs:[i16] ;call original int 16h pushf ;save flags jz exit16 ;no key in buffer - depart cmp al,0 ;alt key pressed? jne exit16 ;no - depart cmp ah,cs:hotkey ;our hot key pressed? jne exit16 ;no - depart mov ah,0 ;remove key from buffer call cs:[i16] ;call original int 16h call run_demo ;call our main prog jmp checkchar ;go check buffer exit16: popf ;discard flags ret 2 ;return to caller int16 endp initialize proc mov ax,cs ;get code seg value mov ds,ax ;set DS to same continue: mov ah,9Bh ;set up for int 16 query int 16h ;call it cmp ax,0ABCDh ;is DEMO loaded? jne not_loaded ;no, continue mov dx,offset loaded_msg ;yes, it's loaded mov ah,9 ;set up to write msg int 21h ;write it mov ah,4Ch ;terminate int 21h not_loaded: mov ax,3567h ;set up to get int 67h seg int 21h ;call DOS mov di,10 ;offset of EMM string mov si,offset emm_name ;offset of our string mov cx,8 ;8 chars to check cld ;set direction flag forward repz cmpsb ;compare string jz emm_ok ;compare ok? mov dx,offset emm_msg ;no mov ah,9 ;set up for error msg int 21h ;call DOS to write mov ah,4Ch ;set up to terminate int 21h ;terminate emm_ok: mov ah,41h ;set up to get EMM segment int 67h ;call EMM mov cs:demo_seg,bx ;save it mov es,bx ;put it in ES mov ax,es:[loaded_in_emm] ;get DEMO flag cmp ax,9876h ;is it there? je demo_present ;yes mov dx,offset not_loaded_msg ;no mov ah,9 ;set up for error msg int 21h ;call DOS to write mov ah,4Ch ;set up to terminate int 21h ;terminate demo_present: mov al,byte ptr es:[activate] ;get hot key mov hotkey,al ;save it mov ax,word ptr es:[emm_handle] ;get EMM handle mov handle,ax ;save it mov ax,word ptr es:[demo_main];get DEMO handler offset mov demo_ofs,ax ;save it mov ax,3516h ;set up to get int16 addr int 21h ;call DOS to get it mov i16_seg,es ;save segment mov i16_ofs,bx ;save offset mov ax,2516h ;set up to replace with ours mov dx,offset int16 ;offset into DX int 21h ;call DOS to install mov dx,offset sign_on ;sign on msg offset mov ah,9 ;set up to write int 21h ;call DOS to write mov dx,offset initialize ;last byte of resident code int 27h ;terminate & stay resident emm_name db 'EMMXXXX0',0 emm_msg db 'No EMM available - aborting',7,'$' loaded_msg db 'KERNEL in memory - aborting',7,'$' sign_on db 'KERNEL is loaded and DEMO is operational in EMS','$' not_loaded_msg db 'DEMO not in expanded memory',7,'$' initialize endp code ends end begin