Microsoft Programmer's Library 1.3

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Assembly Source File | 1988-08-11 | 9.4 KB | 270 lines

TITLE CH1.ASM ; CH1.ASM -- support file for CTERM.C terminal emulator ; set up to work with COM2 ; for use with Microsoft C and SMALL model only... _TEXT segment byte public 'CODE' _TEXT ends _DATA segment byte public 'DATA' _DATA ends CONST segment byte public 'CONST' CONST ends _BSS segment byte public 'BSS' _BSS ends DGROUP GROUP CONST, _BSS, _DATA assume cs:_TEXT, DS:DGROUP, ES:DGROUP, SS:DGROUP _TEXT segment public _i_m,_rdmdm,_Send_Byte,_wrtmdm,_set_mdm,_u_m bport EQU 02F8h ; COM2 base address, use 03F8H for COM1 getiv EQU 350Bh ; COM2 vectors, use 0CH for COM1 putiv EQU 250Bh imrmsk EQU 00001000b ; COM2 mask, use 00000100b for COM1 oiv_o DW 0 ; old int vector save space oiv_s DW 0 bf_pp DW in_bf ; put pointer (last used) bf_gp DW in_bf ; get pointer (next to use) bf_bg DW in_bf ; start of buffer bf_fi DW b_last ; end of buffer in_bf DB 512 DUP (?) ; input buffer b_last EQU $ ; address just past buffer end bd_dv DW 0417h ; baud rate divisors (0=110 bps) DW 0300h ; code 1 = 150 bps DW 0180h ; code 2 = 300 bps DW 00C0h ; code 3 = 600 bps DW 0060h ; code 4 = 1200 bps DW 0030h ; code 5 = 2400 bps DW 0018h ; code 6 = 4800 bps DW 000Ch ; code 7 = 9600 bps _set_mdm proc near ; replaces BIOS 'init' function PUSH BP MOV BP,SP ; establish stackframe pointer PUSH ES ; save registers PUSH DS MOV AX,CS ; point them to CODE segment MOV DS,AX MOV ES,AX MOV AH,[BP+4] ; get parameter passed by C MOV DX,BPORT+3 ; point to Line Control Reg MOV AL,80h ; set DLAB bit (see text) OUT DX,AL MOV DL,AH ; shift param to BAUD field MOV CL,4 ROL DL,CL AND DX,00001110b ; mask out all other bits MOV DI,OFFSET bd_dv ADD DI,DX ; make pointer to true divisor MOV DX,BPORT+1 ; set to high byte first MOV AL,[DI+1] OUT DX,AL ; put high byte into UART MOV DX,BPORT ; then to low byte MOV AL,[DI] OUT DX,AL MOV AL,AH ; now use rest of parameter AND AL,00011111b ; to set Line Control Reg MOV DX,BPORT+3 OUT DX,AL MOV DX,BPORT+2 ; Interrupt Enable Register MOV AL,1 ; Receive type only OUT DX,AL POP DS ; restore saved registers POP ES MOV SP,BP POP BP RET _set_mdm endp _wrtmdm proc near ; write char to modem _Send_Byte: ; name used by main program PUSH BP MOV BP,SP ; set up pointer and save regs PUSH ES PUSH DS MOV AX,CS MOV DS,AX MOV ES,AX MOV DX,BPORT+4 ; establish DTR, RTS, and OUT2 MOV AL,0Bh OUT DX,AL MOV DX,BPORT+6 ; check for on line, CTS MOV BH,30h CALL w_tmr JNZ w_out ; timed out MOV DX,BPORT+5 ; check for UART ready MOV BH,20h CALL w_tmr JNZ w_out ; timed out MOV DX,BPORT ; send out to UART port MOV AL,[BP+4] ; get char passed from C OUT DX,AL w_out: POP DS ; restore saved regs POP ES MOV SP,BP POP BP RET _wrtmdm endp _rdmdm proc near ; reads byte from buffer PUSH BP MOV BP,SP ; set up ptr, save regs PUSH ES PUSH DS MOV AX,CS MOV DS,AX MOV ES,AX MOV AX,0FFFFh ; set for EOF flag MOV BX,bf_gp ; use "get" ptr CMP BX,bf_pp ; compare to "put" JZ nochr ; same, empty INC BX ; else char available CMP BX,bf_fi ; at end of bfr? JNZ noend ; no MOV BX,bf_bg ; yes, set to beg noend: MOV AL,[BX] ; get the char MOV bf_gp,BX ; update "get" ptr INC AH ; zero AH as flag nochr: POP DS ; restore regs POP ES MOV SP,BP POP BP RET _rdmdm endp w_tmr proc near MOV BL,1 ; wait timer, double loop w_tm1: SUB CX,CX ; set up inner loop w_tm2: IN AL,DX ; check for requested response MOV AH,AL ; save what came in AND AL,BH ; mask with desired bits CMP AL,BH ; then compare JZ w_tm3 ; got it, return with ZF set LOOP w_tm2 ; else keep trying DEC BL ; until double loop expires JNZ w_tm1 OR BH,BH ; timed out, return NZ w_tm3: RET w_tmr endp ; hardware interrupt service routine rts_m: CLI PUSH DS ; save all regs PUSH AX PUSH BX PUSH CX PUSH DX PUSH CS ; set DS same as CS POP DS MOV DX,BPORT ; grab the char from UART IN AL,DX MOV BX,bf_pp ; use "put" ptr INC BX ; step to next slot CMP BX,bf_fi ; past end yet? JNZ nofix ; no MOV BX,bf_bg ; yes, set to begin nofix: MOV [BX],AL ; put char in buffer MOV bf_pp,BX ; update "put" ptr MOV AL,20h ; send EOI to 8259 chip OUT 20h,AL POP DX ; restore regs POP CX POP BX POP AX POP DS IRET _i_m proc near ; install modem service PUSH BP MOV BP,SP ; save all regs used PUSH ES PUSH DS MOV AX,CS ; set DS,ES=CS MOV DS,AX MOV ES,AX MOV DX,BPORT+1 ; Interrupt Enable Reg MOV AL,0Fh ; enable all ints now OUT DX,AL im1: MOV DX,BPORT+2 ; clear junk from UART IN AL,DX ; read IID reg of UART MOV AH,AL ; save what came in TEST AL,1 ; anything pending? JNZ im5 ; no, all clear now CMP AH,0 ; yes, Modem Status? JNZ im2 ; no MOV DX,BPORT+6 ; yes, read MSR to clear IN AL,DX im2: CMP AH,2 ; Transmit HR empty? JNZ im3 ; no (no action needed) im3: CMP AH,4 ; Received Data Ready? JNZ im4 ; no MOV DX,BPORT ; yes, read it to clear IN AL,DX im4: CMP AH,6 ; Line Status? JNZ im1 ; no, check for more MOV DX,BPORT+5 ; yes, read LSR to clear IN AL,DX JMP im1 ; then check for more im5: MOV DX,BPORT+4 ; set up working conditions MOV AL,0Bh ; DTR, RTS, OUT2 bits OUT DX,AL MOV AL,1 ; enable RCV interrupt only MOV DX,BPORT+1 OUT DX,AL MOV AX,GETIV ; get old int vector INT 21h MOV oiv_o,BX ; save for restoring later MOV oiv_s,ES MOV DX,OFFSET rts_m ; set in new one MOV AX,PUTIV INT 21h IN AL,21h ; now enable 8259 PIC AND AL,NOT IMRMSK OUT 21h,AL MOV AL,20h ; then send out an EOI OUT 20h,AL POP DS ; restore regs POP ES MOV SP,BP POP BP RET _i_m endp _u_m proc near ; uninstall modem service PUSH BP MOV BP,SP ; save registers IN AL,21h ; disable COM int in 8259 OR AL,IMRMSK OUT 21h,AL PUSH ES PUSH DS MOV AX,CS ; set same as CS MOV DS,AX MOV ES,AX MOV AL,0 ; disable UART ints MOV DX,BPORT+1 OUT DX,AL MOV DX,oiv_o ; restore original vector MOV DS,oiv_s MOV AX,PUTIV INT 21h POP DS ; restore registers POP ES MOV SP,BP POP BP RET _u_m endp _TEXT ends END