513 lines
12 KiB
NASM
513 lines
12 KiB
NASM
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; Copyright (C) 1989 by Manx Software Systems, Inc.
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;:ts=8
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;------------------------------------------------------------
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; Module:
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; pcio.asm
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;
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; Description:
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; PCIO, which is linked into both RDB and the monitor,
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; accesses the serial port on behalf of the packet routines.
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;
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; These routines assume that both programs are running on IBM PC-type
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; systems. The routines can be initialized to access either COM1 or COM2,
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; and can drive the serial line at any rate up to the maximum 115k baud.
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;
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; The PCIO routines usually access the serial port using "sense-status"
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; loops instead of interrupts. The only time serial interrupts are enabled
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; is on the target system, when the user program is executing. Then the
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; serial interrupt allows the host system's operator to break into the
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; execution of the user program.
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;
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; During receipt of a packet, interrupts are disabled. This is needed
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; to achieve high data transmission rates.
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; A disadvantage is that all interrupts,
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; including those of the clock and keyboard, are disabled on the receiving
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; system during receipt of a packet.
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;
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; PCIO can be used in both small code and large code programs.
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;
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; Special equates:
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; MODEL Defines pcio's memory model (used by procdef macro).
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; ALLOW_INT 1=Allow break into executing program.
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; 0=Don't allow break.
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;
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;------------------------------------------------------------
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include lmacros.h
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dataseg segment word public 'data'
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BASE equ 3f8H ;COM1's base port address
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; Serial port registers:
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; These are stored as DW's rather than EQU's, so that they can be
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; changed to use COM2's addresses during syytem startup, if desired.
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DATA dw BASE+0 ;data register
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INTENAB dw BASE+1 ;interrupt enable register
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DIVLAT dw BASE+0 ;divisor latch (least sig. byte)
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INTID dw BASE+2 ;interrupt identification register
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LINECTL dw BASE+3 ;line control register
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MODCTL dw BASE+4 ;modem control register
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LINSTAT dw BASE+5 ;line status register
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MODSTAT dw BASE+6 ;modem status register
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;
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; 8259 Interrupt controller information:
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;
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INTNUM db 12 ;COM1 interrupt vector #
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INTMASK db 10H ;bit mask for 8259.
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INTCTL equ 20h ;8259 control register
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INTCHIP equ 21h ;8259 mask register
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i db 0
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vec_save dd ?
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intr_reg db ?
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intr_chp db ?
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dataseg ends
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assume cs:codeseg, ds:dataseg
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codeseg segment
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;---------------------------------------------------------
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; Procedure:
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; FirstThing_
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;
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; Purpose:
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; Do special initialization, after reset and before any other system
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; initialization. When FirstThing is entered, no other initialization
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; has yet been done. In particular, the dataseg segment hasn't been
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; initialized, bss segment hasn't been cleared, and the DS, ES, SS segment
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; registers haven't been set up.
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;
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; Input:
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; None.
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;
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; Output:
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; None.
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;
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; Changes:
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; AX, DX, DS
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;---------------------------------------------------------
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procdef FirstThing
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pret
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pend FirstThing
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;---------------------------------------------------------
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; Procedure:
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; comPutChar_
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;
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; Purpose:
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; Output one byte.
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;
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; Input:
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; The byte to be sent is on the stack.
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;
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; Output:
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; The byte is sent to the serial port.
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;
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; Changes:
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; AX.
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;---------------------------------------------------------
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procdef comPutChar,<<outvalue,word>>
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push dx
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mov dx,LINSTAT
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comput1: ;wait until transmitter is ready
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in al,dx
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and ax,20H
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jz comput1
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mov ax,outvalue ;get caller's char.
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mov dx,DATA
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out dx,al ;output the data
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pop dx
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pret
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pend comPutChar
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;---------------------------------------------------------
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; Procedure:
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; comGetChar_
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;
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; Purpose:
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; Input one byte.
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;
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; Input:
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; None.
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;
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; Return values:
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; Carry flag: Set if error occurred, reset if not.
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; AH: -1 if an error occurred, 0 if not.
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; AL: Line status if error occurred, input byte if not.
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;
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; Changes:
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; AX, DX.
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;---------------------------------------------------------
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procdef comGetChar
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mov dx,LINSTAT
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comGC1:
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in al,dx
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and al,15 ;check for data avail & errors
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jz comGC1 ;loop until something happens
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test al,14 ;check for errors
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jnz comGC_err
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mov dx,DATA
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in al,dx ;get the character
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xor ah,ah ;Make result positive to report
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;no error to C callers.
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clc ;Clear carry to report no error
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;to asm callers.
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pret
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comGC_err:
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mov ah,-1 ;Make AX negative to report an error
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;to C callers.
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stc ;Set carry to report an error
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;to asm callers.
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pret
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pend comGetChar
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;---------------------------------------------------------
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; Procedure:
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; comGetBunch_
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;
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; Purpose:
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; Called by GetPacket() to read some characters from the serial line.
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;
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; Input:
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; CX = number of characters to read.
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; ES:DI = Pointer to location where characters are to be placed.
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;
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; Output:
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; - The input characters are stored in the place pointed at by ES:DI.
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; - Return values:
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; ES:DI Address of the byte following the last stored byte.
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; Carry flag
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; Set if an error occurred.
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; Reset if no error.
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; AX Line status. (0 if no error).
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;
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; Changes:
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; AX, DX.
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;
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; Notes:
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; Interrupts are disabled while in comGetBunch. For low transmission
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; rates (e.g. 9600 and lower) interrupts could be enabled and still
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; not lose data.
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;---------------------------------------------------------
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procdef comGetBunch
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cld
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GB0:
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mov dx,LINSTAT
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GB1:
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in al,dx
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and al,15 ;check for data avail & errors
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jz GB1 ;loop until something happens
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test al,14 ;check for errors
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jnz GBerr
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mov dx,DATA
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in al,dx ;get the character
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stosb ;save the received char
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loop GB0
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clc ;say no error occurred
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xor ax,ax
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pret
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; Come here if an input error occurs.
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GBerr:
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xor ah,ah ;AX = line status
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stc
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pret ;return error to caller
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pend comGetBunch
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;---------------------------------------------------------
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; Procedure:
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; comStatus_
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;
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; Purpose:
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; Get status of COM port.
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;
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; Input:
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; None.
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;
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; Output:
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; The low order four bits of the serial port's line status register
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; are returned in AX.
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;
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; Changes:
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; AX, DX
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;---------------------------------------------------------
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procdef comStatus
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xor ah,ah
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mov dx,LINSTAT
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in al,dx
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and al,15
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pret
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pend comStatus
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;---------------------------------------------------------
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; Procedure:
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; comInit_
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;
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; Purpose:
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; Initialize COM port.
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;
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; Input:
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; baud rate - The word on the stack that's just above the
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; return address. This is normally the actual baud rate;
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; e.g. 9600, 1200. But there are two special values:
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; 0 - Don't send baud rate selection to serial port.
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; 1 - Set baud rate to 115k baud.
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; serial port - The serial port to use. 1 signifies COM1, 2 COM2.
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;
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; Output:
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; None.
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;
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; Changes:
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; AX, BX, CX, DX
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;---------------------------------------------------------
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procdef comInit, <<speed,word>,<channel,word>>
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cmp channel,1
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je skipfix
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;
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; we are using SERIAL2, adjust I/O ports, and Int vectors
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;
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mov bx,offset DATA
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mov al,2
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fixloop:
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mov byte ptr 1[bx],al
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add bx,2
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cmp bx,offset MODSTAT
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jbe fixloop
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dec INTNUM ;serial2 uses IRQ3
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shr INTMASK,1
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skipfix:
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mov dx,INTENAB ;get contents of interupt enable reg.
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in al,dx
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mov intr_reg,al ;sav contents of interupt enable reg.
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mov al,0 ;disable interupts
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out dx,al
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ifdef ROM
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; Initialize the 8259 chip for a PC clone-type system
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; First send Initialization command words
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mov al,13h ;ICW1: edge, sngl, icw4
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out INTCTL,al
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mov al,8 ;ICW2: IRQ0 is interrupt 8
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out INTCHIP,al
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mov al,9 ;ICW4: buffrd, 8086 mode
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out INTCHIP,al
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; Now send operation control word 1
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mov al,0ffh ;mask off all but COM1 interrupts
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; mov al,INTMASK ;mask off all but COM1 interrupts
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out INTCHIP,al
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; The following isn't needed:
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; mov al,20h ;signal EOI to interrupt controller
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; out INTCTL,al
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endif
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cmp speed,0
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je nosetup
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cmp speed, 1 ;special case check for 115200 baud
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jne cominit1
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mov al,80H
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mov dx,LINECTL
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out dx,al
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mov ax,1
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jmp cominit2
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cominit1:
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mov al,80H
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mov dx,LINECTL
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out dx,al
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mov ax,0c200H
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mov dx,1 ;dividend = 0x1c200
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div speed ;compute baud rate divisor
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cominit2:
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mov dx,DIVLAT
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out dx,al ;setup com port to given baud rate
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mov al,ah
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inc dx ;second byte of divisor latch
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out dx,al
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nosetup:
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; clear any pending interrupts
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mov dx,DATA
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in al,dx ;just in case one was waiting for us
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mov dx,LINSTAT
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in al,dx ;clear status interrupts
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mov dx,MODSTAT
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in al,dx
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; setup line and modem control registers
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mov al,03H ;set 8 data, 1 stop, no parity
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mov dx,LINECTL
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out dx,al
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mov dx,MODCTL
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mov al,03h ;turn on DTR, RTS, disable serial interrupts
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out dx,al
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pret
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pend comInit
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;---------------------------------------------------------
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; Procedure:
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; comRestore
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;
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; Purpose:
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; Restore com port to original condition.
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; This is done by setting the 8259 registers back to their
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; initial state.
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;
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; Input:
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; None.
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;
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; Output:
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; The 8259 is set back in its original state.
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;
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; Changes:
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; AX, DX.
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;---------------------------------------------------------
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procdef comRestore
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mov al,intr_reg
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mov dx,INTENAB
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out dx,al
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if 0
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mov al,intr_chp
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mov dx,INTCHIP
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out dx,al
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endif
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pret
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pend comRestore
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;---------------------------------------------------------
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; Procedure:
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; comIsrSet
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;
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; Purpose:
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; Set the serial interrupt vector.
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; This routine is called by the monitor, before control of the
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; processor is passed to the user program, in order to allow the host
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; operator to break into the user program.
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;
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; Input:
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; CS:AX - The new serial interrupt vector.
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;
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; Output:
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; The serial interrupt vector is modified.
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;
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; Changes:
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; None.
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;---------------------------------------------------------
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dataseg segment
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saveser dw 0,0
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dataseg ends
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procdef comIsrSet
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ifdef ALLOW_INT
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push dx
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push bx ;save registers
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push es
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push ax
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mov bx,0 ;point es:bx at serial vector
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mov es,bx
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mov bl,INTNUM
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shl bx,1
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shl bx,1
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mov ax,es:[bx] ;save current vector in saveser
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mov saveser,ax
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mov ax,es:[bx+2]
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mov saveser+2,ax
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mov ax,cs ;set CS:AX in vector
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mov es:[bx+2],ax
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pop ax
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mov es:[bx],ax
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; enable serial interrupts on the 8250
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mov dx,LINECTL ;clear any pending serial ints
|
||
|
|
in al,dx
|
||
|
|
mov dx,DATA
|
||
|
|
in al,dx
|
||
|
|
mov dx,MODCTL
|
||
|
|
mov al,0bh ;turn on DTR, RTS, and allow ints
|
||
|
|
out dx,al
|
||
|
|
mov dx,INTENAB ;interrupt on receipt of character
|
||
|
|
mov al,1
|
||
|
|
out dx,al
|
||
|
|
; enable serial interrupts on the 8259
|
||
|
|
mov dx,INTCHIP ;get contents of interupt chip
|
||
|
|
in al,dx
|
||
|
|
mov intr_chp,al ;sav contents of interupt chip
|
||
|
|
mov cl,INTMASK
|
||
|
|
not cl
|
||
|
|
and al,cl
|
||
|
|
out dx,al ;turn on interupt chip
|
||
|
|
; restore registers and return
|
||
|
|
pop es ;restore regs
|
||
|
|
pop bx
|
||
|
|
pop dx
|
||
|
|
endif
|
||
|
|
pret ;return to caller
|
||
|
|
pend comIsrSet
|
||
|
|
;---------------------------------------------------------
|
||
|
|
; Procedure:
|
||
|
|
; comIsrReset
|
||
|
|
;
|
||
|
|
; Purpose:
|
||
|
|
; Reset the serial interrupt vector to the value it had before
|
||
|
|
; comIsrSet was called.
|
||
|
|
;
|
||
|
|
; Input:
|
||
|
|
; None.
|
||
|
|
;
|
||
|
|
; Output:
|
||
|
|
; The serial interrupt vector is restored.
|
||
|
|
;
|
||
|
|
; Changes:
|
||
|
|
; None.
|
||
|
|
;---------------------------------------------------------
|
||
|
|
procdef comIsrReset
|
||
|
|
ifdef ALLOW_INT
|
||
|
|
push es ;save registers
|
||
|
|
push dx
|
||
|
|
push bx
|
||
|
|
push ax
|
||
|
|
mov bx,0 ;point es:bx at vector
|
||
|
|
mov es,bx
|
||
|
|
mov bl,INTNUM
|
||
|
|
shl bx,1
|
||
|
|
shl bx,1
|
||
|
|
mov ax,saveser ;restore saved vector
|
||
|
|
mov es:[bx],ax
|
||
|
|
mov ax,saveser+2
|
||
|
|
mov es:[bx+2],ax
|
||
|
|
; disable serial interrupts on the 8250
|
||
|
|
mov dx,INTENAB
|
||
|
|
mov al,0
|
||
|
|
out dx,al
|
||
|
|
mov dx,MODCTL
|
||
|
|
mov al,3 ;turn on just DTR, RTS
|
||
|
|
out dx,al
|
||
|
|
; disable serial interrupts on the 8259
|
||
|
|
mov al,intr_chp
|
||
|
|
mov dx,INTCHIP
|
||
|
|
out dx,al
|
||
|
|
; restore registers and return
|
||
|
|
pop ax ;restore registers
|
||
|
|
pop bx
|
||
|
|
pop dx
|
||
|
|
pop es
|
||
|
|
endif
|
||
|
|
pret
|
||
|
|
pend comIsrReset
|
||
|
|
;---------------------------------------------------------
|
||
|
|
; Procedure:
|
||
|
|
; comIsrClear_
|
||
|
|
;
|
||
|
|
; Purpose:
|
||
|
|
; Clear the serial input port, after interrupt
|
||
|
|
;
|
||
|
|
; Input:
|
||
|
|
; None.
|
||
|
|
;
|
||
|
|
; Output:
|
||
|
|
; None.
|
||
|
|
;
|
||
|
|
;---------------------------------------------------------
|
||
|
|
procdef comIsrClear
|
||
|
|
ifdef ALLOW_INT
|
||
|
|
push dx
|
||
|
|
push ax
|
||
|
|
mov dx,DATA ;flush the input port
|
||
|
|
in al,dx
|
||
|
|
mov al,20h ;signal EOI to interrupt controller
|
||
|
|
out INTCTL,al
|
||
|
|
pop ax
|
||
|
|
pop dx
|
||
|
|
endif
|
||
|
|
pret
|
||
|
|
pend comIsrClear
|
||
|
|
|
||
|
|
codeseg ends
|
||
|
|
end
|