HT45F23 datasheet(29/152 Pages) HOLTEK

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Memory Pointers

- MP0, MP1

Two Memory Pointers, known as MP0 and MP1 are provided. These Memory Pointers are physically

implemented in the Data Memory and can be manipulated in the same way as normal registers

providing a convenient way with which to address and track data. When any operation to the relevant

Indirect Addressing Registers is carried out, the actual address that the microcontroller is directed to, is

the address specified by the related Memory Pointer. MP0, together with Indirect Addressing Register,

IAR0, are used to access data from Bank 0, while MP1 and IAR1 are used to access data from all banks

according to BP register. Direct Addressing can only be used with Bank 0, all other Banks must be

addressed indirectly using MP1 and IAR1.

The following example shows how to clear a section of four Data Memory locations already defined as

locations adres1 to adres4.

Indirect Addressing Program Example

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:

The important point to note here is that in the example shown above, no reference is made to specific

Data Memory addresses.

HT45F23/HT45F43

8-Bit Flash MCU with Op Amps & Comparators

Rev. 1.20

September 15, 2011

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