HT45F75 datasheet(34/190 Pages) HOLTEK

34 / 190 page

Rev. 1.10

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HT45F75

Body Fat Scale Flash MCU

HT45F75

Body Fat Scale Flash MCU

Special Function Register Description

MostoftheSpecialFunctionRegisterdetailswillbedescribedintherelevantfunctionalsection,

howeverseveralregistersrequireaseparatedescriptioninthissection.

Indirect Addressing Registers – IAR0, IAR1, IAR2

TheIndirectAddressingRegisters,IAR0,IAR1andIAR2,althoughhavingtheirlocationsinnormal

RAMregisterspace,donotactuallyphysicallyexistasnormalregisters.Themethodofindirect

addressingforRAMdatamanipulationusestheseIndirectAddressingRegistersandMemory

Pointers,incontrasttodirectmemoryaddressing,wheretheactualmemoryaddressisspecified.

ActionsontheIAR0,IAR1andIAR2registerswillresultinnoactualreadorwriteoperationto

theseregistersbutrathertothememorylocationspecifiedbytheircorrespondingMemoryPointers,

MP0,MP1L/MP1HorMP2L/MP2H.Actingasapair,IAR0andMP0cantogetheraccessdataonly

fromSector0whiletheIAR1registertogetherwiththeMP1L/MP1HregisterpairandIAR2register

togetherwiththeMP2L/MP2HregisterpaircanaccessdatafromanyDataMemorySector.As

theIndirectAddressingRegistersarenotphysicallyimplemented,readingtheIndirectAddressing

Registerswillreturnaresultof“00H”andwritingtotheregisterswillresultinnooperation.

Memory Pointers – MP0, MP1L, MP1H, MP2L, MP2H

FiveMemoryPointers,knownasMP0,MP1L,MP1H,MP2L,MP2H,areprovided.TheseMemory

PointersarephysicallyimplementedintheDataMemoryandcanbemanipulatedinthesameway

asnormalregistersprovidingaconvenientwaywithwhichtoaddressandtrackdata.Whenany

operationtotherelevantIndirectAddressingRegistersiscarriedout,theactualaddressthatthe

microcontrollerisdirectedtoistheaddressspecifiedbytherelatedMemoryPointer.MP0,together

withIndirectAddressingRegister,IAR0,areusedtoaccessdatafromSector0,whileMP1L/MP1H

togetherwithIAR1andMP2L/MP2HtogetherwithIAR2areusedtoaccessdatafromallsectors

accordingtothecorrespondingMP1HorMP2Hregister.DirectAddressingcanbeusedinall

sectorsusingthecorrespondinginstructionwhichcanaddressallavailabledatamemoryspace.

ThefollowingexampleshowshowtoclearasectionoffourDataMemorylocationsalreadydefined

aslocationsadres1toadres4.

Indirect Addressing Program Example 1

data .section ´data´

adres1 db ?

adres2 db ?

adres3 db ?

adres4 db ?

block db ?

code .section at 0 ´code´

org 00h

start:

mov a, 04h

; setup size of block

mov block, a

mova,offsetadres1 ;AccumulatorloadedwithfirstRAMaddress

movmp0,a;setupmemorypointerwithfirstRAMaddress

loop:

clrIAR0 ;clearthedataataddressdefinedbyMP0

inc mp0

; increment memory pointer

sdz block

; check if last memory location has been cleared

jmp loop

continue:

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