HT67F60 datasheet(43/242 Pages) HOLTEK

43 / 242 page

HT67F30/HT67F40/HT67F50/HT67F60

TinyPowerTM A/D Flash Type 8-Bit MCU with LCD & EEPROM

Rev. 1.50

March 06 , 2012

Rev. 1.50

March 06 , 2012

Special Function Register Description

Most of the Special Function Register details will be described in the relevant functional section;

however several registers require a separate description in this section.

Indirect Addressing Registers – 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. Note that for the HT67F30

device, bit 7 of the Memory Pointers is not required to address the full memory space. When bit 7 of

the Memory Pointers for HT67F30 device is read, a value of “1” will be returned.

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

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:

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

RAM addresses.

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