MPXM2010D datasheet(15/24 Pages) FREESCALE

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AN1950

Sensors

Freescale Semiconductor

bne try10

ldhx #msg02c

;if $02

bra showit

try10: cmp #$01

bne try0

ldhx #msg02b

;if $01

bra showit

try0:

ldhx #msg02a

;otherwise this one

showit: jsr lcdstro

jsr del1s

;1s between pressure/altitude readings

brset 1,porta,contin ;exit only if SEL

brset 2,porta,contin ;and ENT pressed together

jmp MENU

contin: jmp LVLwarm

;__________________________________________________________

LfNx:

sub N1

;*** PX=f(NX,N2,N1) ***

ldx UnitType

;$A0=160 for cm, $3F=63 for in

mul

sta NA

stx NB

clr NC

;NCNBNA:=(NX-N1)* (conversion value: 160 or 63)

lda N2

sub N1

sta DA

clr DB

clr DC

jsr NdivD

;RBRA:=(NX-N1)*(conversion value)/(N2-N1)

lda RA

cmp #$C8

;check to see if result is negative

bcs noovflw

;if <$C8 we are OK

ovflw: clr RA

;otherwise force level to 0!

noovflw: lda RA

rts

;__________________________________________________________

NdivD: clr RA

;RBRA:=NCNBNA/DCDBDA

clr RB

;destroys NCNBNA and DCDBDA

keepatit: lda RA

add #$01

sta RA

lda RB

adc #$00

sta RB

;increment RB:RA

lda NA

sub DA

sta NA

lda NB

sbc DB

sta NB

lda NC

sbc DC

sta NC

;NC:NB:NA:=NC:NB:NA-DC:DB:DA

bcc keepatit

;keep counting how many times until overflow

lda RA

sub #$01

sta RA

lda RB

sbc #$00

sta RB

;we counted once too many, so undo that

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