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CALIBRATING THE RC OSCILLATOR OF THE ST7FLITE0 MCU USING THE MAINS

nocarry sub

A, (capture1,Y);MSB are in register X

jrnc

noneg

;

dec

X

;and LSB in register A.

noneg

inc

Y

cp

Y,#$4

jrne

calcul

srl

A

;these lines calculate the average of the last four

srl

X

;measures by dividing their total by 4. It is done by

jrnc

carry1

;two consecutive right shift on the 16 bit result.

add

A,#$80

carry1 srl

A

srl

X

jrnc

carry2

add

A,#$80

carry2 cp

X, #$01

;if mains frequency is 50Hz the reference value is $138

jrmi

minus

;if it is 60Hz the reference is $104.the program first

jreq

compare

;compares MSB with $01 and then compare LSB with

jp

plus

;$38 for 50Hz and $04 for 60Hz. if the calculated

compare cp

A, #$38

;value is smaller than the reference the program jump to

jrmi

minus

;minus to decrease RCCR else it increase RCCR

plus

ld

A, RCCR

add

A, value

;add value if counted value is greater than ref

jp

new

minus

ld

A, RCCR

sub

A, value

;subtract value if Y is smaller

new

ld

RCCR,A

;enter the new value in RCCR

btjf

value, #0, next;stop after 7 rounds

loop

jp

loop

4.2.2 input capture interrupt

ld

A, LTICR

;load captured value in A

btjt

LTCSR, #4, finish

;test if it is first or second capture

bset

LTCSR, #4

;allow timebase interrupt in order to count the

number of overflows

ld

capture1, A

;captured value is stored in capture1

jp

endit1

finish ld

capture2, A

;if it is the second capture, captured value is

stored in capture2

clr

cr

;clear cr to end the count

endit1 iret

4.2.3 timebase interrupt

ld

A, LTCSR

;clear TB bit

inc

nbover

;increment number of overflows

endit2 iret