HT49RA1 datasheet(13/58 Pages) HOLTEK

13 / 58 page

HT49RA1/HT49CA1

Rev. 1.00

May 7, 2008

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 Bank0, while MP1 and IAR1 are used to access

data from Bank0 and Bank1.

The following example shows how to clear a section of four RAM locations already defined as locations adres1 to

adres4.

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 RAM addresses.

Bank Pointer

- BP

In the Data Memory area it should be noted that both the

LCD Memory and the other Data Memory share the

same addresses. Therefore when using instructions to

access the LCD Memory or the General Purpose Data

Memory, it is necessary to ensure that the correct area is

selected. The General Purpose is located in Bank 0

while the LCD Memory is located in Bank 1. Selecting

the correct Data Memory area is achieved by using the

Bank Pointer. If data in Bank 0 is to be accessed then BP

should be cleared to zero, while if the LCD Memory is to

be accessed, which is located in Bank 1, then BP should

be loaded with a value of 01H. It must be noted that data

in Bank 1can only be accessed indirectly using the MP1

Memory Pointer and the IAR1 indirect addressing regis-

ter. Any direct addressing or any indirect addressing us-

ing MP0 and IAR0 will always result in data from Bank 0

being accessed. The Data Memory Bank Pointer is in-

itialised to Bank 0 after a reset, except for the WDT

time-out reset in the Power Down Mode, in which case,

the Data Memory Bank Pointer remains unchanged. It

should be noted that the Special Function Data Memory

is not affected by the bank selection, which means that

the Special Function Registers can be accessed from

within either Bank 0 or Bank 1.

Accumulator

- ACC

The Accumulator is central to the operation of any and

is closely related with operations carried out by the ALU.

The Accumulator is the place where all intermediate re-

sults from the ALU are stored. Without the Accumulator

it would be necessary to write the result of each calcula-

tion or logical operation such as addition, subtraction,

shift, etc., to the Data Memory resulting in higher pro-

gramming and timing overheads. Data transfer opera-

tions usually involve the temporary storage function of

the Accumulator; for example, when transferring data

between one user defined register and another, it is nec-

essary to do this by passing the data through the Accu-

mulator as no direct transfer between two registers is

permitted.

B P R e g i s t e r

b 7

b 0

B P 0

D a t a M e m o r y

B a n k 0

B a n k 1 L C D M e m o r y

N o t u s e d , m u s t b e r e s e t t o " 0 "

Bank Pointer Register

HT49RA1 数据表(PDF) 13 Page - Holtek Semiconductor Inc

HT49RA1 数据表(HTML) 13 Page - Holtek Semiconductor Inc

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HT49RA1 数据表(PDF) 13 Page - Holtek Semiconductor Inc

HT49RA1 数据表(HTML) 13 Page - Holtek Semiconductor Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

数据表 下载

链接网址

数据表下载