хм, и за ЭТО с людей дерут по $200… себестоимость все этого 282руб в ценах chip-and-dip 🙂

;------------------------------------------------------------------------------
; Hondainfo's Speed Limit Defencer
; AT89C4051 mikrokontroller assembly program
; V1.2 2003.10.22
;------------------------------------------------------------------------------

$mod51

;------------------------------------------------------------------------------
; Theory:
;
; The VSS signal (measured data)
; At 60 km/h    Freq: 42 Hz
; At 100 km/h   Freq: 70 Hz
; At 120 km/h   Freq: 84 Hz
; At 170 km/h   Freq: 119 Hz
; duty in all case:50%
;
; This program is a simple signal copy when the frequency of signal is below 119 Hz
; Above 119Hz, the program switches to Virtual mode and sends Virtual
; 119 Hz signals to ECU independ on Input signal frequency.
;
;------------------------------------------------------------------------------
;------------------------------------------------------------------------------
; Memory variables:
;------------------------------------------------------------------------------
; pin definition
VSS_IN  EQU P3.7        ; Recieve VSS signal here
VSS_OUT EQU P1.7        ; artifical VSS signal to ECU (0: transistor is closed, 1: transistor is opened, pull the signal to Gr
VIRTUAL bit 001h        ; mode: =1 Virtual, =0 real signal output
VSS_OLD bit 002h        ; altering of sampled signal
COUNTR  data 030h       ; Real Counter counts the time beetween two VSS signal
COUNTV  data 031h       ; Virtual counter for artifical VSS signal output
;------------------------------------------------------------------------------
; Cнmdeffinition, interrupt table
;------------------------------------------------------------------------------
  RESET code 00000h
  org 0000h                                     ;starting here after Reset
    ljmp kezdet
  org 0003h
    reti
  org 000bh                                     ;Timer 0 interrupt
    ljmp T0_int
  org 0013h
    reti
  org 001bh
    reti
  org 0023h
    reti
  org 002bh
    reti
  org 30h
;------------------------------------------------------------------------------
;       22.1184 Mhz quartz
;       Timer 0 interrupt aprox: 0,0434 ms time base for measuring milisecs
;       - run 23040 times per a second
;       time period: 43 us
;       runing time max: 30 us
;------------------------------------------------------------------------------
T0_int:         PUSH PSW
                mov TL0,#0B0h           ; software reload
                mov TH0,#0FFh
                mov TCON,#050h
;*****MEASURING VSS SIGNAL
                jb VSS_IN,Ti0           ; jump if no signal (1->0 edge)
                jnb VSS_OLD,Ti0         ; jump if previous sample similar
                mov a,#192d             ; there is signal, check the counter
                clr c                   ; 192x0,0434ms=8,33msec (119 Hz)
                subb A,COUNTR
                cpl c                   ; If < = 8,33 msec then switch to virtual signal mode
                mov VIRTUAL,c           ; If > 8.33 msec then switch to Real signal mode
                mov COUNTR,#0ffh        ; Initial Real Counter
Ti0:            mov c,VSS_IN            ; sample altering
                mov VSS_OLD,c
                mov a,COUNTR
                xrl a,#250d             ; increment Real Counter, but max: 250
                jz Ti1
                inc COUNTR
;*****VIRTUAL COUNTER
Ti1:            mov a,COUNTV
                xrl a,#192d             ; increment Virtual Counter 0-192 cycle
                jnz Ti11
                mov COUNTV,#0ffh
Ti11:           inc COUNTV
;*****REAL MODE SIGNAL COPY
Ti2:            jb VIRTUAL,Ti3          ; jump if Virtual mode
                mov c,VSS_IN            ; In Real Mode simple SIGNAL COPY
                cpl c
                mov VSS_OUT,c
                sjmp Ti4
;*****VIRTUAL MODE ARTIFICAL SIGNAL OUTPUT
Ti3:            mov a,#096d             ; Virtual signaling above 170 kph
                clr c                   ; send 0 to output (pull to the ground)
                subb A,COUNTV           ; when Virtual Counter < =96
                cpl c                   ; send 1 to output (release)
                mov VSS_OUT,c           ; when Virtual Counter >96
Ti4:            POP PSW
                reti                    ; END OF INTERRUPT

;------------------------------------------------------------------------------
;Starting after Reset, int init
;------------------------------------------------------------------------------
kezdet:         clr VSS_OUT             ; init output
                mov c,VSS_IN            ; first altering
                mov VSS_OLD,c
                mov COUNTR,#250d
                mov COUNTV,#000d
                clr VIRTUAL
                mov TMOD,#021h          ; init timers T1 mode 2 (Auto Reload, Serial Port)
                mov TL1,#0FFH           ; T0 mode 1 (16 bit timer, software reload, Interrupt)
                mov TH1,#0FFH           ; serial port timing 9600 baud (use for testing)
                mov TL0,#0B0h           ; 65536d-80d-t to the counter init
                mov TH0,#0FFh           ;
                mov SCON,#052H          ; serial port mode 1
                mov TCON,#050h          ; Timer1 , Timer0 indul
                mov IE,#092h            ; RI/TI int enabled, T0 int enabled
ciklus:         sjmp ciklus

end