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Assembly Source File | 1989-05-14 | 12.2 KB | 440 lines

@ab equ 6 ;use big model ; $Id: pc-ints.asm,v 1.6 89/05/06 17:13:38 lee Exp $ ; ; the following constants are hardware specific to the MPU401 & OP4000 ; MIDI interface controllers ; $Log: pc-ints.asm,v $ ; Revision 1.6 89/05/06 17:13:38 lee ; rel. to comp.sources.misc ; ; ; BASE_ADDRESS_MPU equ 330h STATUS_PORT_MPU equ BASE_ADDRESS_MPU + 1 COMMAND_PORT_MPU equ BASE_ADDRESS_MPU + 1 DATA_PORT_MPU equ BASE_ADDRESS_MPU + 0 Tx_EMT equ 40h ;midi transmitter ready for more data Rx_NEMT equ 80h ;midi receiver has data ready MPU_INT equ 2 MPU_INT_MASK equ 4 ; ; the remaining constants are for the AT&T PC6300 and compatible PC's ; TIMER_INT equ 0 TIMER_INT_MASK equ 1 HW_INT_MASK equ MPU_INT_MASK OR TIMER_INT_MASK INT_CTLR_PORT equ 20h ;port to send EOI command to INT_CTLR_IMR equ 21h ;port to mask interrupts EOI_CODE equ 20h ;EOI command T_55MS equ 0000h ; 8253 value for 55 ms T_5MS equ 174dh ; 8253 value for 5 ms TIC_55MS equ 11 ; Number of timer tics to equal 55 ms PIT_MODE equ 36h ; 8253 mode: 00 11 011 0 -> cntr0,LSB/MSB,mode 3,binary PIT_CNT0 equ 40h ; Counter 0 port for 8253 PIT PIT_CTRL equ 43h ; Control port for 8253 PIT USER_TMR equ 1ch ; User Timer (55 ms) Int. Vector ; ;******************** ;** macros ** ;******************** ; c_in macro ;this macro sets up a stack frame push bp ;must save bp reg for 'c' progs mov bp, sp ;set up frame pointer push di push si ;save register vars endm ; c_out macro ;This macro cleans up for return to 'C' pop si pop di mov sp, bp pop bp ;restore caller's frame pointer cld ;clear direction flag ret ;and return endm ; push_all_regs macro push es push ds push dx push cx push bx push si push di push ax push bp endm ; pop_all_regs macro pop bp pop ax pop di pop si pop bx pop cx pop dx pop ds pop es endm ; enable_IMR macro num ;this macro clears (enables) ;interrupts in the interrupt mask reg in al, INT_CTLR_IMR ;read in current int mask and al, 0ffh - num ;clear the requested IMR bit out INT_CTLR_IMR, al ;and write it back out endm ; disable_IMR macro num ;disable interrupts in the IMR in al, INT_CTLR_IMR ;read in current int mask or al, num ;set the requested IMR bit out INT_CTLR_IMR, al ;and write it out endm ; ack_int macro ;this macro sends non-specific EOI ;to the int controller chip in the PC mov al, EOI_CODE out INT_CTLR_PORT, al sti endm ; ;************************************************************ ;** ** ;** DATA GROUP DECLARATION ** ;** ** ;************************************************************ ; dgroup group data data segment word public 'data' assume ds:dgroup ; ; --- The following vars are used to manage a very small stack ; that is used for interrupt enable/disable stacking ; INT_STACK_SIZE equ 8 * 1 int_stack db (INT_STACK_SIZE/8) dup ('intstack') int_stack_pointer dw 0 ; ; --- The following provide a circular character buffer used to ; store data received from the MIDI interface ; BUFFER_SIZE equ 512 _wrt_index dw 0 _rd_index dw 0 _midi_buffer db BUFFER_SIZE dup (0) public _wrt_index public _rd_index public _midi_buffer ; ; --- The following vars are used to keep a running tally of the ; programmable timer ticks. ; _hzcount dd 0 int_cnt dw 0 public _hzcount ; data ends ; ;************************************************************ ;** ** ;** CODE SEGMENT ** ;** ** ;** ** ;************************************************************ ; ; extrn _fatal_dos_handler:far ;'C' routine to handle DOS errors extrn _bye:far ; exit routine for Ctl-brk _code segment byte public 'code' assume cs:_code public _ctl_brk public _asm_fatal_dos_handler public _disable_ints public _enable_ints public _init_enable_MPU public _init_enable_TIMER public _reset_TIMER public _write_data_MPU public _read_MPU public _midi_isr public _tick_isr ; ;************************************************************ ;** ** ;** INTERRUPT HANDLERS ** ;** ** ;** ** ;************************************************************ _ctl_brk proc far ; ; Control-Break Interrupt Service Routine ; ctl_st: cli ; make sure no interrupts mov ax,ds mov ss,ax ; ss = ds :: so chkstk() doesn't fail in quit() mov sp,0fffeh ; and sp = hi mem mov ax,1 ; exit code sti ; turn interrupts back on push ax call _bye pop bp ; not needed, never returns here iret ; or here _ctl_brk endp ; ; Fatal Dos Error Interrupt Service Routine ; _asm_fatal_dos_handler proc far push_all_regs ;save machine state push di push ax ;push args for function mov ax, dgroup mov ds, ax ;address data segment mov es, ax ;and extra segmant call _fatal_dos_handler ;handler(ax, di) pop ax pop ax pop_all_regs mov al,0 ;tell DOS to ignore error iret _asm_fatal_dos_handler endp ; ; ;************************************************************ ;** MIDI_ISR ** ;** This is the MPU int service routine ** ;** It reads data from MPU data port until there is no more** ;** and stores in a circular buffer ** ;************************************************************ ; _midi_isr proc far push_all_regs ;save machine state mov ax, dgroup mov ds, ax disable_IMR MPU_INT_MASK sti do_another: mov dx, DATA_PORT_MPU in al, dx ;read in the interrupt data from MPU inc _wrt_index ;bump up write pointer cmp _wrt_index, 01ffh ;is index at top of buff? jle wrt_index_ok mov _wrt_index, 0 ;if yes, wraparound to bottom wrt_index_ok: ;of buffer mov bx, _wrt_index mov _midi_buffer[bx], al ;move data into buffer mov dx, STATUS_PORT_MPU ;DX = &status port in al, dx ;read status port and al, Rx_NEMT ;is there data to read? jz do_another ;go back if so ;isr return cli ;turn off system ints enable_IMR MPU_INT_MASK ack_int ;and acknowlege interrupt pop_all_regs ;restore machine state iret ;and leave _midi_isr endp ; ;******************************************************************** ;* TICK_ISR ;* The interrupt service routine for the programmable timer. ;* Timer is currently set at 5 ms. intervals. ;******************************************************************** ; _tick_isr proc far ; tmr_st: push ds push ax mov ax, dgroup mov ds, ax ;must have our data segment disable_IMR TIMER_INT_MASK sti add word ptr _hzcount, 1 adc word ptr _hzcount + 2, 0 inc int_cnt cmp int_cnt,TIC_55MS jge tm1 cli enable_IMR TIMER_INT_MASK ack_int pop ax pop ds iret tm1: mov int_cnt,0 int USER_TMR cli enable_IMR TIMER_INT_MASK ack_int pop ax pop ds iret _tick_isr endp ; ;************************************************************ ;** DISABLE_INTS() ** ;** Called to disable interrupts. stacks old int ** ;** status before disabling, so that nesting is ** ;** preserved. ** ;************************************************************ ; _disable_ints proc far cli in al, INT_CTLR_IMR ;read in current int mask mov dl, al ;move it to dl and dl, HW_INT_MASK ;extract the bit for MPU ints mov bx, int_stack_pointer ;get current stack pointer mov int_stack[bx], dl ;store out int status there inc bx mov int_stack_pointer, bx ;write back new stack pointer value or al, HW_INT_MASK ;mask off int out INT_CTLR_IMR, al ;and write it out sti ret _disable_ints endp ; ;************************************************************ ;** ENABLE_INTS() ** ;** Restores whatever the int status was before ** ;** DISABLE_INTS() was called. ** ;** Note that calls to enable and disable must be matched ** ;** or chaos will occur ** ;************************************************************ ; _enable_ints proc far cli in al, INT_CTLR_IMR ;read in current int mask and al, 0ffh - HW_INT_MASK ; get all the bits except the ones ; for out ints mov bx, int_stack_pointer ;get int stack pointer dec bx ;move it down mov int_stack_pointer, bx ;store it or al, int_stack[bx] ;or in int status with old one out INT_CTLR_IMR, al ;and write it out sti ;turn ints on now ret _enable_ints endp ; ;************************************************************ ;** INIT_ENABLE_MPU() ** ;** Starts up the MPU ints. ** ;** ** ;************************************************************ ; _init_enable_MPU proc far cli enable_IMR MPU_INT_MASK sti ret _init_enable_MPU endp ;; ;************************************************************ ;** INIT_ENABLE_TIMER() ** ;** Starts up the TIMER ints. ** ;** ** ;************************************************************ ; _init_enable_TIMER proc far cli ; Set 8253 PIT for different timing ; mov al,PIT_MODE out PIT_CTRL,al ; Set 8253 mode mov ax,T_5MS out PIT_CNT0,al mov al,ah out PIT_CNT0,al ; Set new timing enable_IMR TIMER_INT_MASK sti ret _init_enable_TIMER endp ; ; ;************************************************************ ;** RESET_TIMER() ** ;** Sets timer values back to what they were ** ;** ** ;************************************************************ _reset_TIMER proc far disable_IMR TIMER_INT_MASK mov al,PIT_MODE out PIT_CTRL,al ; Set 8253 mode mov ax,T_55MS out PIT_CNT0,al mov al,ah out PIT_CNT0,al ; Reset timing enable_IMR TIMER_INT_MASK ret _reset_TIMER endp ; ;************************************************************ ;** WRITE_DATA_MPU(DATA) ** ;** sends a byte to the MPU data port ** ;** waits for handshake ** ;** ** ;************************************************************ ; ; _write_data_MPU proc far c_in mov bx, @ab[bp] ;get data byte in bl reg call write_sub ;and call fast sub c_out ;leave _write_data_MPU endp ; ;************************************************************ ;** ** ;** write_sub ** ;** Writes data to MPU. on entry, byte in bl ** ;** ax, cx, cx destroyed ** ;************************************************************ ; write_sub proc near mov dx, STATUS_PORT_MPU ;set up pointer to MPU port write_clear_loop: in al, dx and al, Tx_EMT jnz write_clear_loop dec dx ;point to data reg mov al, bl out dx, al ;send out the data ret write_sub endp ; ;************************************************************ ;** read_MPU() ** ;** reads a byte from the MPU eata port ** ;** waits for handshake ** ;** ** ;************************************************************ ; _read_MPU proc far c_in read_clear_loop: mov dx, STATUS_PORT_MPU ;DX = &status port in al, dx and al, Rx_NEMT jnz read_clear_loop dec dx ;point to data reg in al, dx xor ah, ah c_out _read_MPU endp ; _code ends end