Power Programmierung/Power-Programmierung (Tewi)(1994).iso/assemblr/library/asm_kit/host.asm

Assembly Source File | 1985-11-06 | 17KB | 386 lines

                PAGE    66,132
                TITLE   HOST - Link communication device to console using interrupts
;
;       Program to install resident communications interrupt driver,
;       and link it into the keyboard/video interrupt routines.
;
;       We must define a general interrupt handler for the COM1 port,
;       which will input characters directly into BIOS's keyboard input
;       (typeahead) buffer.  This buffer is defined by pointers at offset
;       001A (start of buffer pointer), and 001C (end of buffer pointer).
;       The data segment for all of this is 0040.  There is a BIOS routine
;       at F000:E875 which handles a 15-char circular buffer wrap-around.
;       We should copy it.  We must compare [001A] with [001C] after calling
;       the buffer wrap routine to see if the buffer full.  If so, it'd
;       be nice to send a bell to the caller, but im not sure this is the
;       place to do it (inside an interrupt routine).
;
;       Note that we assume the COM1 port is already initialized (RS232 stuff)
;
;       Note that this routine must also detect change of line status and
;       have appropriate logic for indicating and handling loss of carrier,
;       and other delta indications in the line status register.
;
;       This takes care of the keyboard input end of the communication
;       interface.
;
;       For linking screen output, I guess we just intercept the old
;       screen output 'interrupt' vector, located at 0000:0040-:0043.
;       There is no reason to buffer the output, so the intercept routine
;       will first output the byte to the UART (if UART accepting), then
;       pass control on to the former screen handler.
;
; The record-type HOSTFLAGS contains duplex, CR/LF, bell enable, and
; timeout specification.  Timeout determines iff forced disconnect for
; lack of user input enablad.
hostflags       record  duplex:1,crlf:1,bell:1,cls:1,timeout:1
discflags       record  rlsd:1,ri:1,dsr:1,cts:1
;
comment %
; Structure HOSTCB contains terminal setting values:
hostcb          struc
clsequence      db      0,12    ; default cls sequence
timeout_at      db      128     ; halfway through the timeout scale default
baudrate_lsb    db      80h
baudrate_msb    db      1       ; default UART baud rate = 300 baud
userid          dt      ?       ; ten bytes?  for user identification
screen_size     db      24      ; # of lines on screen
screen_width    db      80      ; # of chars per line on screen
hostcb          ends
;
%
;
inport          macro   port
                lea     dx,port ; get port offset into dx
                in      al,dx
                endm
;
outport         macro   port
                lea     dx,port ; get port offset into dx
                out     dx,al
                endm
;
; Set up references to the system interrupt vector table:
;
;
int_table       segment at 0h
                org     10H*4           ; address of video driver vector
int10           label   word
                org     0CH*4           ; address of comm interrupt vector
int0c           label   word
int_table       ends
;
; Set up references to BIOS keyboard and COM system table.
;
;
sys_table       segment at 40h
rs232_base      dw      4 dup(?)
                org     1Ah
buffer_head     dw      ?
buffer_tail     dw      ?
kb_buffer       dw      16 dup(?)
kb_buffer_end   label   word
                org     71h
bios_break      db      ?
sys_table       ends
;
;
comgrp          group   host,com_init
;
host            segment
                assume  cs:comgrp
;
; Proc to bump BIOS's keyboard buffer pointer, in DI.
advance_kb      proc    far
                add     di,2
                cmp     di,offset kb_buffer_end
                jnz     noneed
                mov     di,offset kb_buffer     ; wrap if at end of buffer
noneed:         ret
advance_kb      endp
;
eoi             equ     20h     ; end of interrupt value for 8259 controller
;
baud_data       equ     0[BX]   ; baud rate selector and data register in UART
baud_msb_int    equ     1[BX]   ; baud rate selector MSB and interrupt enable
interrupt_id    equ     2[BX]   ; interrupt identification register
line_control    equ     3[BX]   ; line control register
modem_control   equ     4[BX]   ; modem control register
line_status     equ     5[BX]   ; line status register
modem_status    equ     6[BX]   ; modem status register
;
comint          proc    far
                assume  cs:comgrp,ds:sys_table
                sti
                push    ax
                push    bx
                push    cx
                push    dx
                push    si
                push    di
                push    ds
                push    es
                mov     ax,sys_table            ; point to system table segment
                mov     ds,ax
                mov     bx,rs232_base           ; get base port for COM1 device
;
; Begin code to interrogate interrupt situation: "Why were we called ?"
;
; Note that we have set interrupts for change in modem status, and
; receiver data-ready.  This means either he hung up (or ?) or he
; just sent us a character.  The interrupt-id register will tell us which.
;
                inport  interrupt_id    ; read the interrupt id register
                shr     al,1            ; of course an interrupt occurred!
                and     al,00000011b    ; lower 2 bits active.
                jz      delta_stat      ; go interpret change in modm stat
                dec     al              ; test for transmitter hold empty.
                jz      no_action       ; we're not processing these here.
                dec     al              ; test for received char?
                jz      get_com_char    ; read char from com device.
                dec     al              ; Break or error received.
                jz      brk_rcd
no_action:      mov     al,eoi          ; end-of-inerrupt code to al
                out     20h,al          ; tell controller to cancel interrupt
                pop     es
                pop     ds
                pop     di
                pop     si
                pop     dx
                pop     cx
                pop     bx
                pop     ax
                iret                    ; return to previous task.
;
; Break was received (or there was a line error)
; IF break received, simulate console CONTROL-BREAK function.
;
brk_rcd:        inport  line_status
                and     al,00010000b    ; break detected ?
                jz      no_action       ; we're ignoring other errors now.
                mov     di,offset kb_buffer     ; load kb_buffer start
                mov     buffer_head,di  ; reset buffer to empty
                mov     buffer_tail,di
                mov     bios_break,80h  ; set break byte.
                int     1bh             ; do break service
                jmp     no_action       ; return ourselves
;
get_com_char:   inport  baud_data       ; read byte from port
                mov     di,buffer_tail  ; end of kb buff
                mov     si,di           ; store it
                call    advance_kb      ; try to make space for it
                cmp     di,buffer_head  ; has buffer wrapped ?
                jz      kb_full         ; buffer full!
                xor     ah,ah           ; convert al -> ax
                mov     [si],ax         ; store it in BIOS keyboard buffer
                mov     buffer_tail,di  ; update buffer
                jmp     no_action       ; return to caller
;
kb_full:        jmp     no_action       ; we'll eventually BEEP the user here.
;
delta_stat:     inport  modem_status
                mov     cs:c_modem_status,al    ; remember new modem status

                jmp     no_action
;
comint          endp
;
;
console_out     proc    far
                assume  cs:host,ds:sys_table
                jmp     begin_console   ; jump around ID field
console_id:     db      'HOST'          ; our identification field
begin_console:  cmp     ah,14           ; is it 'print tty' function ?
                jz      take_over       ; yes, intercept it
                cmp     ah,10           ; it is 'print over char' function ?
                jz      take_over       ; yes, lets intercept it too
normal_tty:     jmp     cs:old_int10    ; go to normal int 10 handler
take_over:      push    ax
                push    di
                push    si
                push    dx
                push    bx
                push    cx
                push    ds
                test    cs:c_modem_status,10000000b     ; is there a connection?

                jz      bypass_user             ; no, we wont try to send
                mov     cl,al           ; save value for output
                mov     ax,sys_table
                mov     ds,ax           ; prepare to examine UART
                mov     bx,rs232_base   ; get base address of com port
send_char:      inport  line_status     ; see if ready to send byte.
                and     al,00100000b    ; test xmit hold reg empty ?
                jz      send_char       ; no, wait for it
                mov     al,cl           ; get back char to send
                outport baud_data       ; output byte to com1 iff ready
bypass_user:    pop     ds
                pop     cx
                pop     bx
                pop     dx
                pop     si
                pop     di
                pop     ax
                jmp     normal_tty
;
console_out     endp
;
old_int10       dd      ?               ; doubleword pointer to old int10
;
; Set up our internal status flags:
c_modem_status  discflags       <?,?,?,?>
; Set up user parm area
user_flags      hostflags <1,1,1,1,1>   ; user logon and termninal flags
user_disc       discflags <1,0,1,0>     ; lines for continual test/disconnect
;user_parms     hostcb <,,,,,,>         ; user logon and terminal characteristics
user_parms      equ     $
;
; Structure HOSTCB contains terminal setting values:
clsequence      db      0,12    ; default cls sequence
timeout_at      db      128     ; halfway through the timeout scale default
baudrate_lsb    db      80h
baudrate_msb    db      1       ; default UART baud rate = 300 baud
userid          dt      ?       ; ten bytes?  for user identification
screen_size     db      24      ; # of lines on screen
screen_width    db      80      ; # of chars per line on screen
;
end_com         equ     this    byte    ; return to dos, stay res.
;
host            ends
;
com_init        segment
                assume  cs:com_init,ds:sys_table,es:comgrp
host_init       proc    far
;
; We'll assume that the UART has been initialized for now
; we will install the interrupt driven keyboard link and
; the INT 10H intercept driver.
;
                cli                             ; off ints so dont get caught
                push    ds                      ; save pointer to dos psp
                mov     ax,50h                  ; offset to int21 in psp
                push    ax
                mov     ax,host                 ; point to driver segment
                mov     es,ax
                mov     ax,sys_table            ; point to system table
                mov     ds,ax
                mov     bx,rs232_base           ; get base of port addresses
                inport  modem_status
                mov     es:c_modem_status,al    ; initialize out record of it
                mov     al,00001011b            ; set MCR for interrupts
                outport modem_control
                mov     al,00001101b            ; desired interrupt fields
                outport baud_msb_int            ; enable those interrupts
                mov     ax,int_table            ; get interrupt table segment
                mov     ds,ax
                assume  ds:int_table
                mov     dx,int10                ; get offset for old int10
                push    dx
                push    bx
                push    ds
                xchg    bx,dx                   ; put offset into bx
                mov     ax,host                 ; address ID field
                mov     ds,ax
                mov     dx,[bx+3]               ; look at our ID field1
                cmp     dx,'HO'                 ; Could it be us ?
                jnz     notus                   ; nop.
                mov     dx,[bx+5]               ; Look at field 2 to be sure
                cmp     dx,'ST'
notus:          pop     ds
                pop     bx
                pop     dx
                jnz     itsok
                jmp     reject_init             ; We were already installed
itsok:          mov     es:old_int10,dx         ; fill in
                mov     dx,int10+2              ; get segment for old int10
                mov     es:old_int10+2,dx       ; fill in
                mov     dx,host                 ; get new seg for int10
                mov     int10+2,dx              ; store it
                mov     dx,offset console_out   ; get new offset for int10
                mov     int10,dx                ; store it
                mov     dx,host                 ; get new seg for int0c
                mov     int0c+2,dx              ; store it
                mov     dx,offset comint        ; and offset
                mov     int0c,dx                ; and offset
                in      al,21h                  ; read from IMR
                and     al,0efh ; turn off b4=enable comm interrupts
                out     21h,al                  ; in 8259 controller
                mov     al,0                    ; retcode = 0
                mov     dx,offset comgrp:end_com; point to end of program
                mov     cl,4                    ; for devide by 16
                shr     dx,cl                   ; turn into # segments
                add     dx,100                  ; leave 1K for dos environ ????
                mov     ah,31h                  ; tell DOS to save this pgm.
                jmp     ok_init                 ; successful initialization

;
exit_init:      ret                             ; far ret to dos function call
;
ok_init:        sti                             ; re-enable the interrupts
;               call    print_inline
;               db      'pcHOST 1.0 - 09/29/83 - M.R.',13,10
;               db      'Communication console link loaded and initialized.'
;               db      13,10,10,0
                jmp     exit_init
;
reject_init:    sti                             ; re-enable the interrupts
;               call    print_inline
;               db      'HOST driver is already installed.',13,10
;               db      'Nothing done.',13,10,0
;               pop     ax              ; pop off 'stay resident' return
;               xor     ax,ax           ; make 'terminate overlay' return
;               push    ax
                jmp     exit_init
;
; Print_Inline proc:  Prints ASCIIZ text at offset on NEAR STACK.
; Returns to address following delimiting zero of ASCIIZ string.
; Resgisters destroyed: SI.
print_inline    proc
                pop     si
                push    ax
check_char:     mov     al,[si]
                inc     si
                or      al,al
                jz      msg_done
                call    print_chr
                jmp     check_char
msg_done:       pop     ax      ; get back ax
                push    si      ; is this the ONLY way to jump
                ret             ; to an address pointed to by SI ?
print_inline    endp
;
; Print_Chr proc: prints char in AL via INT 10H.
; Registers destroyed:  AX.
print_chr       proc
                mov     ah,14           ; and AH for PRINT TTY function
                call    int_10h         ; print char to tty
                ret
print_chr       endp
;
; INT_10H proc:  Intercept to the BIOS INT 10H
;                but saving all registers.  Also, set BX=0 to select current
;                screen page.  All registers except BX must be set prior call.
;  Registers destroyed: None.
int_10h         proc
                push    bx
                push    ax
                mov     bx,0            ; select screen zero
                push    bp
                push    di
                push    si
                int     10h
                pop     si
                pop     di
                pop     bp
                pop     ax
                pop     bx
                ret
int_10h         endp
;
host_init       endp
com_init        ends
;
;
                end     host_init