HT45F0057 datasheet(17/81 Pages) HOLTEK

17 / 81 page

Rev. 1.30

May 17, 2022

Rev. 1.30

May 17, 2022

HT45F0057

Induction Cooker Flash MCU

HT45F0057

Induction Cooker Flash MCU

Special Function Register Description

Most of the Special Function Register details will be described in the relevant functional sections,

however several registers require a separate description in this section.

Indirect Addressing Register – IAR0, IAR1

The Indirect Addressing Registers, IAR0 and IAR1, although having their locations in normal RAM

for RAM data manipulation uses these Indirect Addressing Registers and Memory Pointers, in

contrast to direct memory addressing, where the actual memory address is specified. Actions on the

IAR0 and IAR1 registers will result in no actual read or write operation to these registers but rather

to the memory location specified by their corresponding Memory Pointers, MP0 or MP1. Acting as a

pair, IAR0 and MP0 can together access data from Bank 0 while the IAR1 and MP1 register pair can

access data from any bank. As the Indirect Addressing Registers are not physically implemented,

reading the Indirect Addressing Registers indirectly will return a result of “00H” and writing to the

registers indirectly will result in no operation.

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.

HT45F0057 Datasheet(PDF) 17 Page - Holtek Semiconductor Inc

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