10/15

CALIBRATING THE RC OSCILLATOR OF THE ST7FLITE0 MCU USING THE MAINS

jrnc

nocarry

;this equation is calculated with 16 bits

inc

X

;

nocarry sub

A, capture1

;MSB are in register X

jrnc

noneg

;

dec

X

;and LSB in register A.

noneg

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

4.1.2 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

4.1.3 timebase interrupt

ld

A, LTCSR

;clear TB bit

inc

nbover

;increment number of overflows

endit2 iret

4.1.4 writing in eeprom

To store final value of RCCR in EEPROM, add theses lines after disabling the timer interrupts

in the main program.

ld

RCCR, A

bset

EECSR,#1

;start to enter value in the EEPROM

ld

$1003,A

;load value of the RCCR in EEPROM

bset

EECSR,#0

;start to write in the EEPROM

wait

btjt

EECSR,#0,wait

;wait for the end of writing in EEPROM