Technotools/Technotools (Chestnut CD-ROM)(1993).ISO/lang_asm/dumbterm/dumbterm.asm

Assembly Source File | 1989-03-20 | 15.4 KB | 635 lines

;«OF4»«RM76»«FD66»«PL55,60,50»«RHA«OF4»«RM76»«MDBO»

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------------------------------------------------------------------
;«MDBO»                     DUMBTERM«MDNM»
; «MDBO»Author:    CJ Dunford«MDNM»
; «MDBO»Rev.:        09/12/83«MDNM»
; «MDBO»Source:    DUMBTERM.ASM«MDNM»
; «MDBO»Object:    DUMBTERM.OBJ«MDNM»
; «MDBO»Code:        DUMBTERM.EXE«MDNM»
; «MDBO»O/S:        PCDOS 1.1, 2.0«MDNM»
;
; Note that the program assumes that the RS232 port is configured
; as COM1.  It will have to be modified to use COM2.  Also,
; the communications parameters are set as 300 baud, 7 data bits,
; 1 stop bit, even parity.  This can be changed--see the INIT
; procedure.  DUMBTERM will easily keep up with 1200 baud or more.
;
; Assembly/link:
;   Assemble: MASM dumbterm;
;   Link:     LINK dumbterm;
;
; Execution:
;   (from DOS prompt): DUMBTERM
;------------------------------------------------------------------

; * * * * * * * * * * * * * * *
;   EQUATES & DEFINITIONS
; * * * * * * * * * * * * * * *

; ----- Define size of buffer
BUFSIZE        equ    4096        ; 4K--can be adjusted

; ----- ASCII codes
LF        equ    0AH        ; Line feed
CR        equ    0DH        ; Carriage return
ESC        equ    1BH        ; Escape

; ----- BIOS calls
RS232           equ    14H        ; RS232 service
kbd_io           equ    16H        ; Keyboard service

; ----- INS8250 ACE registers

THR    equ    3F8H        ; Trans    holding    register (write)
RBR    equ    3F8H        ; Receiver buffer register (read)
IER    equ    3F9H        ; Interrupt enable register
LCR    equ    3FBH        ; Line control register.
                ; Bit 7    of LCR is "DLAB".  DLAB    must
                ; be zero to access THR, RBR, IER.
MCR    equ    3FCH        ; Modem    control    register
LSR    equ    3FDH        ; Line status register
MSR    equ    3FEH        ; Modem    status register


; ----- Comm parameter definition
; Refer    to IBM Tech Ref, page A-20
; See proc INIT    for usage

commparm record    baud:3,    parity:2, stopbits:1, wordbits:2

; Baud rates
B110        equ    000B
B150        equ    001B
B300        equ    010B
B600        equ    011B
B1200        equ    100B
B2400        equ    101B
B4800        equ    110B
B9600        equ    111B

; Parity
no_parity    equ    00B
odd_parity    equ    01B
even_parity    equ    11B

; Stop bits
stop1        equ    0
stop2        equ    1

; Data bits
data7        equ    10B
data8        equ    11B


; * * * * * * * * * * * * * * *
;    MACROS
; * * * * * * * * * * * * * * *

@bioscall MACRO    call_num, parm
;; Generates an 'INT call_num', with parm in AH
    IFNB <parm>
      mov ah,parm
    ENDIF
    int call_num
    ENDM


@doscall MACRO function,parm
;; Generates a DOS function call with parm in AL
    IFNB <parm>
     mov al,parm
    ENDIF
    @bioscall 21H,function
    endm


; * * * * * * * * * * * * * *
;    DATA & STACK SEGMENTS
; * * * * * * * * * * * * * *

data segment para public 'data'

; ----- The string section
sgreeting    db    '--- ONLINE ---',CR,LF,'$'
sgoodbye    db    CR,LF,'--- OFFLINE ---',CR,LF,'$'
serr1        db    '<R>$'    ; RS232    receive    error
serr2        db    '<S>$'    ; RS232    send error
serr3        db    '<B>$'    ; Receive buffer overflow error

; ----- Flags
brcv_err    db    0    ; Nonzero on RS232 receive error
boverflow    db    0    ; Nonzero on buffer overflow
bdoneflag    db    0    ; Nonzero after ESC from kbd

; ----- Received data buffer and associated pointers
; >> Buffer is empty if head pointer = tail pointer
wbufhead    dw    buffer    ; Pointer to head of buffer
wbuftail    dw    buffer     ; Pointer to tail of buffer
buffer        db    BUFSIZE dup (?)
bufend        equ $
data ends

; ----- Stack
stack segment para stack 'stack'
    db    256 dup (?)
stack ends


; * * * * * * * * * * * * *
;     PROGRAM MAINLINE
; * * * * * * * * * * * * *

code    segment    para public 'code'
    assume cs:code, ds:data, ss:stack

main    proc far

; ----- Initialize
    push ds            ; Set up long ret to DOS
    sub ax,ax
    push ax
    call init        ; Rest of initialization

; ----- Main program loop
M100:
    call buffer_check       ; Check RS232 bfr. Display if not empty
    call kb_check           ; Check kbd. Send to RS232.
    test bdoneflag,0FFH    ; Non-zero if done
    jz M100            ; Loop till ESC received

; ----- ESC received.  Clean up interrupt & exit
    call cleanup        ; Clean    up
    ret            ; Return to DOS
main    endp


; * * * * * * * * * * * * * * *
;     PRIMARY BLOCKS
; * * * * * * * * * * * * * * *

; -----    INIT ------------------------------
; Program initialization:
;   -- Set up RS232
;   -- Set up vector for RS232 interrupt (INT 0CH)
;   -- Enable IRQ4
;   -- Enable RS232 interrupt on data ready
;
; NOTE: The communications parameters are established
; here.  To use other parameters, change the parameters
; in the 'mov al,commparm' statement below.  See the
; communications parameters record definition (above)
; for the correct abbreviations.
;
; Examples:
;   1200,N,8,1:    mov al,commparm <B1200,no_parity,stop1,data8>
;   4800,O,7,2: mov al,commparm <B4800,odd_parity,stop2,data7>
; -----------------------------------------

init proc near

; ----- Initialize RS232: 300,8,N,1
    mov dx,0            ; COM1
    mov al,commparm    <B300,no_parity,stop1,data8>
    @bioscall RS232,0

; ----- Set up INT x'0C' for IRQ4
    cli                ; Interrupts off during    setup
    push ds                ; Save DS
    mov dx,offset ISR        ; Point    to RS232 ISR in    DS:DX
    push cs
    pop ds
    @doscall 25H,0CH        ; Set int vctr for IRQ4
    pop ds                ; Restore DS

; ----- Enable IRQ4 on 8259 interrupt controller
    in al,21H            ; Get current masks
    and al,11101111B        ; Reset    IRQ4 mask
    out 21H,al            ; And restore to IMR

; ----- Enable 8250 data ready interrupt
    mov dx,LCR            ; DX ==> LCR
    in al,dx                        ; Reset DLAB for IER access
    and al,01111111B
    out dx,al
    mov dx,IER            ; Address IER
    mov al,00000001B        ; Enable 'data-ready' interrupt
    out dx,al

; ----- Enable OUT2 on 8250
    mov dx,MCR             ; Address MCR
    mov al,00001000B        ; Enable OUT2
    out dx,al
    sti

; ----- Display greeting & return
    mov ax,data            ; Establish data seg address
    mov ds,ax
    mov dx,offset sgreeting        ; Point to greeting
    call strdisp            ; Display it
    ret
init endp


; ---- BUFFER_CHECK -----------------------
; RS232 buffer check
;
; This block checks the received data buffer.
; It functions as follows:
;
; IF the RS232 input buffer is not empty
;    Get the first character
;    Display the character
;    Update buffer pointer
; IF the RS232 receive error flag is nonzero
;    Display an error indicator
; IF the buffer overflow flag is nonzero
;    Display an error indicator
;
; Entry:
;  No requirement
; Exit:
;  AX, BX, DX destroyed
; -----------------------------------------

buffer_check proc near

; ----- Check buffer status
    mov bx,wbufhead            ; Buffer head pointer
    cmp bx,wbuftail            ; Buffer empty if head = tail
    je BC100            ; Jump if empty

; ----- Something in buffer--get 1st char, fix pointers
    mov al,[bx]            ; Get the char
    call incptr            ; Bump buffer head pointer
    mov wbufhead,bx

; ----- Display character received.  Filter CR/LF
    cmp al,LF            ; Is it a line feed?
    je BC100            ; Skip display if yes
    call chdisp            ; Display if no
    cmp al,CR            ; Is it a CR?
    jne BC100             ; Jump if not
    mov al,LF            ; Send LF if yes
    call chdisp

; ----- Test RS232 receive status; display errors
BC100:
    test brcv_err,0FFH        ; Flag nonzero if errors
    jz BC200            ; Jump if no errors
    mov dx,offset serr1        ; Point to error msg
    call strdisp
    mov brcv_err,0            ; Clear error flag

; ----- Test for buffer overflow; display errors
BC200:
    test boverflow,0FFH
    jz BC300            ; Z if no overflow
    mov boverflow,0            ; Clear the flag
    mov dx,offset serr3        ; Point to error msg
    call strdisp            ; And display

BC300:
    ret
buffer_check endp

; ----- KB_CHECK --------------------------
; Check keyboard.  Functions as follows:
;
; Check the keyboard status
; IF a character is available
;   IF the character is ESC
;      set the 'done' flag
;   ELSE
;      send it to RS232 and watch for errors
;
; Note that this routine does not echo the KB characters
; to the display.   Display occurs only when the characters
; are echoed back by the remote terminal.
;
; Entry:
;  No requirement
; Exit:
;  AX, DX destroyed
; -----------------------------------------

kb_check proc near

; -----    Poll keyboard, check chars received
    call kb_poll                    ; Poll the keyboard
    jz KBC900            ; Kbd clear, exit
    cmp al,ESC            ; Escape?
    jne KBC100            ; No, continue
    mov bdoneflag,0FFH        ; Yes, set termination flag
    jmp short KBC900

; ----- Send the received char, watch for errors
KBC100:
    call RS232_out            ; Send it
    test ah,80H            ; Time out?
    jz KBC900            ; No, sent OK
    mov dx,offset serr2        ; Point to error msg
    call strdisp            ; And display it

KBC900:
    ret
kb_check endp


; -----    ISR -------------------------------
; This is the RS232 interrupt service routine.  It
; is entered whenever the RS232 port interrupts on a
; 'data ready' condition.  The routine simply reads
; the data from the asynch chip and stuffs it in the
; buffer.  Note that the process of reading the
; received data register in the 8250 clears IRQ4.
; However, the 8259 must be told specifically that the
; interrupt service is complete.
;
; This replaces the function 2 of BIOS interrupt 14H
; (receive a character over the comm line).  Since
; it cannot return errors in a register, it puts the
; error marker in memory at 'brcv_err'.  The error
; flag is 'sticky'--a successful read will NOT clear a
; prior error indication.  This allows the program
; mainline to examine the error status at its
; leisure.  Error bits are the same as in RS232OUT,
; above, except that ONLY the error bits are set,
; and bit 7 is not used (always 0).  In other words,
; brcv_err is nonzero only on an error.  Timeout
; errors are not possible here.
;
; The ISR will set the overflow flag if the buffer
; should overflow.  Shouldn't happen.
; -----------------------------------------

ISR    proc near
    sti            ; Allow    other interrupts
    push ax            ; Save all regs used
    push bx
    push dx
    push si
    push ds

; ----- Establish data addressability
    mov ax,data
    mov ds,ax

; ----- Get error bits
    mov dx,LSR        ; Base address of RS232
    in al,dx        ; Get status
    and al,00011110B    ; Mask non-error bits
    jz ISR010        ; Skip error set if OK
    mov brcv_err,al        ; Set error indicator

; ----- Get incoming character and buffer it
ISR010:
    mov dx,RBR        ; Receiver buffer
    in al,dx        ; Get input character
    mov bx,wbuftail        ; Buffer input pointer
    mov si,bx        ; Save pointer b4 increment
    call incptr        ; Bump input pointer
    cmp bx,wbufhead        ; Overflow if head = tail
    je ISR020        ; Overflow
    mov [si],al        ; No overflow, save char in buffer
    mov wbuftail,bx        ; And new input    pointer
    jmp short ISR999
ISR020:
    mov boverflow,0FFH    ; Set overflow flag

; ----- Signal end of interrupt to 8259
ISR999:
    cli
    mov al,20H        ; Non-specific EOI
    out 20H,al        ; Send it

; ----- Restore regs & return.  IRET reenables interrupts
    pop ds
    pop si
    pop dx
    pop bx
    pop ax
    iret
ISR    endp


; ----- CLEANUP --------------------------
; End of program housekeeping
;   -- Disable IRQ4
;   -- Disable 8250 interrupts
;   -- Disable OUT2
;   -- Display offline message
; ----------------------------------------

cleanup    proc near

; ----- Disable IRQ4 on 8259
    cli
    in al,21H            ; IMR
    or al,00010000B            ; Mask bit 4--IRQ4
    out 21H,al

; ----- Disable 8250 data ready interrupt
    mov dx,LCR            ; DX ==> LCR
    in al,dx                        ; Reset DLAB for IER access
    and al,01111111B
    out dx,al
    mov dx,IER            ; Address IER
    mov al,0            ; Disable all 8250 interrupts
    out dx,al

; ----- Disable OUT2 on 8250
    mov dx,MCR             ; Address MCR
    mov al,0            ; Disable OUT2
    out dx,al
    sti

; ----- Display bye-bye
    mov dx,offset sgoodbye
    call strdisp
    ret
cleanup    endp


; * * * * * * * * * * * * * * * *
;    I/O & GENERAL SUBROUTINES
; * * * * * * * * * * * * * * * *

; -----    KB_POLL ---------------------------
; Set/reset Z flag on keyboard buffer status.
;
; Entry:
;  No requirements
; Exit:
;  Z = 1 if nothing available
;  Z = 0 if char available from kbd
;  IF Z = 0
;    AL = char
;    AH = scan code
; Other regs preserved
; -----------------------------------------

kb_poll proc near
    @bioscall kbd_io,1    ; Poll KB. Sets    Z flag if KB bfr empty
    jz KB999        ; Nothing there
    pushf                   ; Save flag status
    @bioscall kbd_io,0    ; Something there; get it
    popf
KB999:
    ret
kb_poll endp



; --- RS232_out --------------------------
; RS232 output routine
;
; This routine sends one character to the RS232 port.
; It replaces function 1 of BIOS int 14H.  This is
; necessary because BIOS will disable the RS232
; interrupt (by disabling OUT2) every time it is
; called.
;
; Entry:
;  AL = character to be transmitted
; Exit:
;  AH = send status
;    Bit 7 = 1 if RS232 timeout occurred
;    IF bit 7 = 0
;       bit 6: trans shift register empty
;       bit 5: trans holding register empty
;       bit 4: break detect
;       bit 3: framing error
;       bit 2: parity error
;       bit 1: overrun error
;       bit 0: data ready
;  Other regs preserved
; ----------------------------------------

RS232_out proc near
    push bx            ; Save regs used
    push cx
    push dx

; ----- Set up RS232
    mov bl,al        ; Save char to BL temporarily
    mov dx,MCR        ; Modem    Control    Register
    mov al,00001011B    ; OUT2,    DTR, RTS
    out dx,al
    sub cx,cx        ; Initialize timeout count
    mov dx,MSR        ; Modem    Status Register

; ----- Wait for DSR
RS100:
    in al,dx
    test al,20H        ; Data set ready?
    jnz RS150        ; Yes
    loop RS100        ; No, retry till timeout
    mov ah,80H        ; Set timeout
    jmp short RSXIT        ; And quit

; ----- Wait for CTS
RS150:
    sub cx,cx        ; Another timeout count
RS200:
    in al,dx
    test al,10H        ; Clear    to send?
    jnz RS250        ; Yes
    loop RS200        ; No, loop till    timeout
    mov ah,80H        ; Timeout, set flag
    jmp short RSXIT        ; And quit

; ----- Wait for THRE
RS250:
    mov dx,LSR        ; Line Status Register
    sub cx,cx        ; Yet another timeout count
RS300:
    in al,dx        ; LSR status
    test al,20H        ; Transmit holding reg empty?
    jnz RS350        ; Yes
    loop RS300        ; No, loop till    timeout
    mov ah,80H        ; Timeout, set flag
    jmp short RSXIT

; ----- Get line status, send char
RS350:
    mov ah,al        ; Get line status for return
    and ah,01111111B    ; Mask out bit 7
    mov al,bl        ; Restore char to AL
    mov dx,THR        ; Trasnmit holding register
    out dx,al        ; Output it to RS232
RSXIT:
    pop dx
    pop cx
    pop bx
    ret
RS232_out endp



; ----- CHDISP ----------------------------
; Display the character in AL on the CRT
; Entry:
;  AL = char
; Exit:
;  All regs restored
; -----------------------------------------

chdisp proc near
    push ax
    push dx
    mov dl,al
    @doscall 2
    pop dx
    pop ax
    ret
chdisp endp



; ----- STRDISP ---------------------------
; Display the string at DS:DX on the CRT
; Entry:
;  DS:DX ==> string
; Exit:
;  All regs restored
; -----------------------------------------

strdisp proc near
    push ax
    @doscall 9
    pop ax
    ret
strdisp endp



; ----- INCPTR ----------------------------
; Increment the buffer pointer in reg BX.
; If the pointer goes beyond the end of the
; buffer, wrap around to start.
;
; Entry:
;  BX = buffer pointer
; Exit:
;  BX = advanced buffer pointer
;  Other regs restored
; -----------------------------------------

incptr proc near
    inc bx                ; Bump pointer
    cmp bx,offset bufend        ; Past end?
    jne IP100            ; Jump if not
    mov bx,offset buffer            ; Else point to start
IP100:
    ret
incptr    endp
code ends
    end main