HT95R64 datasheet(17/82 Pages) HOLTEK

17 / 82 page

HT95R64/HT95R65

Rev. 1.00

March 3, 2010

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. Acting as a

pair, IAR0 and MP0 can together only access data from

Bank 0, while the IAR1 and MP1 register pair can ac-

cess data from both Bank 0 and Bank 1. As the Indirect

Addressing Registers are not physically implemented,

reading the Indirect Addressing Registers indirectly will

return a result of

²00H² and writing to the registers indi-

rectly will result in no operation.

Memory Pointer

- MP0, MP1

For all devices, 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 pro-

viding a convenient way with which to address and track

data. When any operation to the relevant Indirect Ad-

dressing Registers is carried out, the actual address that

the microcontroller is directed to, is the address speci-

fied by the related Memory Pointer. MP0, together with

Indirect Addressing Register, IAR0, are used to access

data from Bank 0 only, while MP1 and IAR1 are used to

access data from Banks 1~10.

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

The Data Memory RAM is divided into eleven banks, known as Bank 0~Bank 10. All of the Special Purpose Registers

are contained in Bank 0. Selecting the required Data Memory area is achieved using the Bank Pointer. If data in Bank 0

is to be accessed, then the BP register must be loaded with the value

²00², while if data in Bank 1 is to be accessed,

then the BP register must be loaded with the value

²01² and so on for the other registers. Using Memory Pointer MP0

and Indirect Addressing Register IAR0 will always access data from Bank 0, irrespective of the value of the Bank

Pointer.

B P 3 , B P 2 , B P 1 , B P 0

D a t a M e m o r y

1 0

1 1 ~ 1 5

N o t i m p l e m e n t e d , r e a d a s " 0 "

8 K R O M b a n k s e l e c t b i t

( N o t e : T h i s b i t i s f i x e d a t " 0 " f o r H T 9 5 R 5 4 )

N o t i m p l e m e n t e d , r e a d a s " 0 "

B a n k P o i n t e r

b 7

b 0

B P 0

B a n k 0

B a n k 1

B a n k 2

B a n k 3

B a n k 4

B a n k 5

B a n k 6

B a n k 7

B a n k 8

B a n k 9

B a n k 1 0

N o t i m p l e m e n t e d

B P 1

B P 2

B P 3

B P 5

Bank Pointer

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