HT37B90 datasheet(16/80 Pages) HOLTEK

16 / 80 page

HT37B90/HT37B70/HT37B50/HT37B30

Rev.1.00

June22,2017

pointer registers MP0, MP1and MP2, where MP1/MP2

can deal with all banks of data memory but MP0 deal

withBank0datamemoryonly.

GeneralPurposeDataMemory

All microcontroller programs require an area of

read/write memory where temporary data can be stored

and retrieved for use later. It is this area of RAM memory

that is known as General Purpose Data Memory. This

area of Data Memory is fully accessible by the user pro-

gram for both read and write operations. The bank 0

data memory areas can handle arithmetic, logic, incre-

ment, decrement and rotate operations directly. By us-

ing the

²SET [m].i² and ²CLR [m].i² instructions

individual bits can be set or reset under program control

giving the user a large range of flexibility for bit manipu-

lationintheDataMemory.

SpecialPurposeDataMemory

This area of Data Memory is where registers, necessary

for the correct operation of the microcontroller, are

stored. such as timers, interrupts, etc., as well as exter-

nal functions such as I/O data control and A/D converter

operation. Most of the registers are both readable and

writable but some are protected and are readable only,

the details of which are located under the relevant Spe-

cial Function Register section. Note that for locations

that are unused, any read instruction to these addresses

will return the value

²00H². Although the Special Pur-

pose Data Memory registers are located in Bank 0, they

will still be accessible even if the Bank Pointer has se-

lectedBank1.

SpecialFunctionRegisters

To ensure successful operation of the microcontroller,

certain internal registers are implemented in the RAM

Data Memory area. These registers ensure correct op-

eration of internal functions such as timers, interrupts,

watchdog, etc., as well as external functions such as I/O

data control. The location of these registers within the

RAMDataMemorybeginsattheaddress

²00H².

IndirectAddressingRegister - IAR0,IAR1

The Indirect Addressing Registers, IAR0 and IAR1, al-

though having their locations in normal RAM register

space, do not actually physically exist as normal regis-

ters. The method of indirect addressing for RAM data

manipulation uses these Indirect Addressing Registers

and Memory Pointers, in contrast to direct memory ad-

dressing, where the actual memory address is speci-

fied. 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 corre-

sponding Memory Pointer, MP0 or MP1/MP2. Acting as

a pair, IAR0 and MP0 can together only access data

from Bank 0, while the IAR1 and MP1/MP2 register can

access data form Bank 0 to Bank 7. Using MP1 or MP2

are selected by DACC.7. As the Indirect Addressing

Registers are not physically implemented, reading the

Indirect Addressing Registers indirectly will return a re-

sult of

²00H² and writing to the registers indirectly will re-

sultinnooperation.

MemoryPointer - MP0,MP1,MP2

Three Memory Pointers, known as MP0, MP1 and MP2

are provided. These Memory Pointers are physically im-

plemented in the Data Memory and can be manipulated

in the same way as normal registers providing a conve-

nient way with which to address and track data. When

any operation to the relevant Indirect Addressing Regis-

ters 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 only, while MP1/MP2 and IAR1 are used to

access data form Bank 0 to Bank 7. Using MP1 or MP2

areselectedby DACC.7.

HT37B90 Datasheet(PDF) 16 Page - Holtek Semiconductor Inc

HT37B90 Datasheet(HTML) 16 Page - Holtek Semiconductor Inc

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