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; irq_test.a51 -- First interrupt srvice test.

;

; This program is meant to run on a light53 MCU with the 16-bit timer. It can be

; run on simulation or in actual hardware.

; Its purpose is to demonstrate the working of the interrupt service logic. No

; actual tests are performed (other than the co-simulation tests), only checks.

;

;-------------------------------------------------------------------------------

        ; Include the definitions for the light52 derivative

        $nomod51

        $include (light52.mcu)

ext_irq_ctr     set     060h        ; Incremented by external irq routine

        ;-- Macros -------------------------------------------------------------

        ; putc: send character in A to console (UART)

putc    macro   character

        local   putc_loop

        mov     SBUF,character

putc_loop:

        ;mov     a,SCON

        ;anl     a,#10h

        ;jz      putc_loop

        endm

        ; put_crlf: send CR+LF to console

put_crlf macro

        putc    #13

        putc    #10

        endm

        ;-- Reset & interrupt vectors ------------------------------------------

        org     00h

        ljmp    start               ;

        org     03h

        ljmp    irq_ext

        org     0bh

        ljmp    irq_timer

        org     13h

        ljmp    irq_wrong

        org     1bh

        ljmp    irq_wrong

        org     23h

        ljmp    irq_wrong

        ;-- Main test program --------------------------------------------------

        org     30h

start:

        ; Disable all interrupts.

        mov     IE,#00

        ;---- External interrupt test --------------------------------------

        ; Trigger external IRQ with IRQs disabled, it should be ignored.

        mov     P1,#01h

        nop

        nop

        nop

        mov     a,ext_irq_ctr

        cjne    a,#00,fail_unexpected

        setb    EXTINT0.0           ; Clear external IRQ flag

        ; Trigger timer IRQ with external IRQ enabled but global IE disabled

        mov     IE,#01h

        mov     P1,#01h

        nop

        nop

        nop

        mov     a,ext_irq_ctr

        cjne    a,#00,fail_unexpected

        setb    EXTINT0.0          ; Clear timer IRQ flag

        ; Trigger external IRQ with external and global IRQ enabled

        mov     P1,#00h

        mov     IE,#81h

        mov     ext_irq_ctr,#00

        mov     P1,#01h

        nop

        nop

        nop

        mov     a,ext_irq_ctr

        cjne    a,#01,fail_expected

        setb    EXTINT0.0          ; Clear timer IRQ flag

        ; End of irq test, print message and continue

        mov     DPTR,#text2

        call    puts

        ;---- Timer test ---------------------------------------------------

        ; Assume the prescaler is set for a 20ms count period

        mov     IE,#000h

        mov     TSTAT,#00

        mov     TH,#00

        mov     TL,#00

        mov     TCH,#0c3h           ; Compare register = 50000 = 1 second

        mov     TCL,#050h

        mov     TSTAT,#030h         ; Start counting

        ; Ok, now wait for a little less than 20us and make sure TH:TL has not

        ; changed yet.

        mov     r0,#95              ; We need to wait for 950 clock cycles...

loop0:                              ; ...and this is a 10-clock loop

        nop

        djnz    r0,loop0

        mov     a,TH

        cjne    a,#000h,fail_timer_error

        mov     a,TL

        cjne    a,#000h,fail_timer_error

        ; Now wait for another 100 clock cycles and make sure TH:TL has already

        ; changed.

        mov     r0,#10              ; We need to wait for 100 clock cycles...

loop1:                              ; ...and this is a 10-clock loop

        nop

        djnz    r0,loop1

        mov     a,TH

        cjne    a,#000h,fail_timer_error

        mov     a,TL

        cjne    a,#001h,fail_timer_error

        ; End of timer test, print message and continue

        mov     DPTR,#text5

        call    puts

        ;-- End of test program, enter single-instruction endless loop

quit:   ajmp    $

fail_timer_error:

        mov     DPTR,#text4

        call    puts

        mov     IE,#00h

        ajmp    $

        ; Did not get expected IRQ: print failure message and block.

fail_expected:

        mov     DPTR,#text3

        call    puts

        mov     IE,#00h

        ajmp    $

        ; Got unexpected IRQ: print failure message and block.

fail_unexpected:

        mov     DPTR,#text1

        call    puts

        mov     IE,#00h

        ajmp    $

;-- puts: output to UART a zero-terminated string at DPTR ----------------------

puts:

        mov     r0,#00h

puts_loop:

        mov     a,r0

        inc     r0

        movc    a,@a+DPTR

        jz      puts_done

        putc    a

        sjmp    puts_loop

puts_done:

        ret

;-- irq_timer: interrupt routine for timer -------------------------------------

; Note we don't bother to preserve any registers

irq_ext:

        mov     P1,#00h             ; Remove the external interrupt request

        mov     EXTINT0,#0ffh       ; Clear all external IRQ flags

        inc     ext_irq_ctr         ; Increment irq counter

        mov     DPTR,#text0         ; Print IRQ message...

        call    puts

        reti                        ; ...and quit

irq_timer:

irq_wrong:

        ajmp    irq_wrong

text0:  db      '',13,10,00h,00h

text1:  db      'Unexpected IRQ',13,10,00h,00h

text2:  db      'IRQ test finished, no errors',13,10,0

text3:  db      'Missing IRQ',13,10,0

text4:  db      'Timer error',13,10,0

text5:  db      'Timer test finished, no errors',13,10,0

        end