HT82B42R datasheet(22/86 Pages) HOLTEK

22 / 86 page

Rev. 1.00

October 27, 2011

Rev. 1.00

October 27, 2011

HT82B42R/HT82B42RE

I/O MCU with USB Interface

Memory Pointer – MP0, MP1

Foralldevices,twoMemoryPointers,knownasMP0andMP1areprovided.TheseMemory

PointersarephysicallyimplementedintheDataMemoryandcanbemanipulatedinthesameway

asnormalregistersprovidingaconvenientwaywithwhichtoaddressandtrackdata.Whenany

operationtotherelevantIndirectAddressingRegistersiscarriedout,theactualaddressthatthe

microcontrollerisdirectedto,istheaddressspecifiedbytherelatedMemoryPointer.MP0canonly

accessdatainBank0whileMP1canaccessbothbanks.

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

mov a,offset adres1

; Accumulator loaded with first RAM address

mov mp0,a

; setup memory pointer with first RAM address

loop:

clr IAR0

; clear the data at address defined by MP0

inc mp0

; increment memory pointer

sdz block

; check if last memory location has been cleared

jmp loop

continue:

Theimportantpointtonotehereisthatintheexampleshownabove,noreferenceismadetospecific

DataMemoryaddresses.

Accumulator – ACC

TheAccumulatoriscentraltotheoperationofanymicrocontrollerandiscloselyrelatedwith

operationscarriedoutbytheALU.TheAccumulatoristheplacewhereallintermediateresults

fromtheALUarestored.WithouttheAccumulatoritwouldbenecessarytowritetheresultof

eachcalculationorlogicaloperationsuchasaddition,subtraction,shift,etc.,totheDataMemory

resultinginhigherprogrammingandtimingoverheads.Datatransferoperationsusuallyinvolve

thetemporarystoragefunctionoftheAccumulator;forexample,whentransferringdatabetween

oneuserdefinedregisterandanother,itisnecessarytodothisbypassingthedatathroughthe

Accumulatorasnodirecttransferbetweentworegistersispermitted.

Program Counter Low Register – PCL

Toprovideadditionalprogramcontrolfunctions,thelowbyteoftheProgramCounterismade

accessibletoprogrammersbylocatingitwithintheSpecialPurposeareaoftheDataMemory.By

manipulatingthisregister,directjumpstootherprogramlocationsareeasilyimplemented.Loading

avaluedirectlyintothisPCLregisterwillcauseajumptothespecifiedProgramMemorylocation,

however,astheregisterisonly8-bitwide,onlyjumpswithinthecurrentProgramMemorypageare

permitted.Whensuchoperationsareused,notethatadummycyclewillbeinserted.

HT82B42R Datasheet(PDF) 22 Page - Holtek Semiconductor Inc

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