In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Staryi wrote:

Bean, I find the interesting thing. This bug is occurs only at 20 MHz and lower! On 50 or 40 Mhz this bug not detected. On 30 - sometimes. On 20 and lower - always!
This is one more version of bug demo program. It counts errors, and shows errcnt on RA.(0..3).


[code]
; Demonstrate the inc/dec bug without debugger (next version)
; Need 4 LED connected from RA.(0..3) to GND 
; (whis current limiter resistor, of course)
; When right work, LEDs don't light
; When this bug occur, the LEDs shows 4 bits of error counter
; Use internal clock oscillator at 32 kHz. 

  

DEVICE  SX48,OSC32KHZ
;DEVICE  SX48,OSCHS3
 

;FREQ 20000000 ; May be any from 32 kHz up to 20 MHz - uncomment if work with debugger 

IRC_CAL IRC_SLOW 

  

RESET start
        org 0x0a
count1  ds 1 ; Two counters
count2  ds 1 ;
errcnt  ds 1 ; error counter 

  

        org 0
; Interrupt service routine (very dummy)
        reti 

  

start   page main
        jmp main 

main
        mov W,#0x1f  ; DDIR_W mode
        mov M,W      ;
        Mov !RA,#11110000b ; RA.(0..3) for output
        clr errcnt   ; errcnt = 0
        Mov RTCC,#0
        Mov !option,#10001000b ; RTCC start
        jmp @Work 

  

        org 0x800
 

; Critically routine 

Work    clr count1    ; count1 = count2 = 0
        clr count2    ;
:loop   inc count1    ; Counters increment
        inc count2    ;
;if is no bug, count1 and count2 must be equal here
        nop           ; for odd loop clocks (9)
        mov W,count1  ; Compare counters
        xor W,count2  ;
        snz           ;
         jmp :loop    ; Infinite loop if equal
        inc errcnt    ; if not - count errors
        Mov RA,errcnt ; Show errcnt
        jmp Work  ; Repeat 

  

        end 
[/code]

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