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Software examples

AN2326

10/20

4

Software examples

A zip file attached to this application note contains the complete software of this calibration

method.

4.1

Single alternance

This version performs only one count between two edges and changes the value of the

RCCR/SICSR registers according to this measurement. This can lead to bad tuning if there

is noise on the reference signal.

4.1.1

Main program

;All the bytes from locations 80h to 85h are used by this software to store values or as control

registers but they can be reused safely after the clock has been set.

;dichotomy value

.value

equ

$81

;this byte contains the value which will be added or

subtracted to/from the RCCR last value at the end of each round

;capture values

.capture1

equ

$82

.capture2

equ

$83

;these two bytes contain the two values of the counter captured on

the edge of the mains, they are used to calculate the time elapsed between the two edges

;number of overflows

.nbover

equ

$84

;this byte contains the number of counter overflows during the

measurement

;control register

.cr

equ

$85

;this byte is used as a control register for the measurement. Its

bits allow or not the interrupts and show which step of the count is the current one.

.strtstp

equ

1

;this is set to start the count and reset to stop it

.lsb_RCCR

equ

7

;this bit is set when the first capture has occurred. It allows

the overflows to be counted

;address to program in NVM (optional)

.E2ADDR

equ $86

.RAM

equ $88

.main

ld A, #$63

ld AVDTHCR, A

; set internal clock to fRC/8 meaning 1MHz targeted

clr SICSR

; clear the 2 lowest significant bits located in this register

ld

A, #$80

;value containing the value which will be

ld

value, A

;add or subs to/from RCCR during the dichotomy

ld

RCCR, A

;RCCR is set to the middle of its range of value

clr

cr

;clear the byte use as control register for the count

next

clr

nbover

;clear the byte containing the number of timer overflow

ld

A, LTICR

;clear the ICF bit

rim

;interrupts enable

bset

LTCSR, #7

;enable input capture interrupt

bset

cr,#strtstp

;set the start-stop bit of cr: count can start

count

btjt cr, #strtstp, count; wait for the end of count

clr

LTCSR

;lite timer interrupts disable

srl

value

;dichotomy value divided by 2

ld

A,#$F9

;these lines calculate this equation:

ld

X,nbover

;

mul

X,A

;(nbover*$F9)+ capture2 - capture1

add

A, capture2

;

jrnc

nocarry

;this equation is calculated with 16 bits

inc

X

;