HT48R065 datasheet(20/93 Pages) HOLTEK

20 / 93 page

HT48R063/064/065/066/0662/067

Rev. 1.10

June 9, 2009

· 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.

Accumulator

- ACC

The Accumulator is central to the operation of any

microcontroller and is closely related with operations

carried out by the ALU. The Accumulator is the place

where all intermediate results from the ALU are stored.

Without the Accumulator it would be necessary to write

the result of each calculation or logical operation such

as addition, subtraction, shift, etc., to the Data Memory

resulting in higher programming and timing overheads.

Data transfer operations usually involve the temporary

storage function of the Accumulator; for example, when

transferring data between one user defined register and

another, it is necessary to do this by passing the data

through the Accumulator as no direct transfer between

two registers is permitted.

Program Counter Low Register

- PCL

To provide additional program control functions, the low

byte of the Program Counter is made accessible to pro-

grammers by locating it within the Special Purpose area

of the Data Memory. By manipulating this register, direct

jumps to other program locations are easily imple-

mented. Loading a value directly into this PCL register

will cause a jump to the specified Program Memory lo-

cation, however, as the register is only 8-bit wide, only

jumps within the current Program Memory page are per-

mitted. When such operations are used, note that a

dummy cycle will be inserted.

Bank Pointer

- BP

In the HT48R0662 and HT48R067 devices, the Data

Memory is divided into two Banks, known as Bank 0 and

Bank 1. A Bank Pointer, which is bit 0 of the Bank Pointer

bank. Only data in Bank 0 can be directly addressed as

data in Bank 1 must be indirectly addressed using Mem-

ory Pointer MP1 and Indirect Addressing Register IAR1.

Using Memory Pointer MP0 and Indirect Addressing

spective of the value of the Bank Pointer. Memory

Pointer MP1 and Indirect Addressing Register IAR1 can

indirectly address data in either Bank 0 or Bank 1 de-

pending upon the value of the Bank Pointer.

The Data Memory is initialised to Bank 0 after a reset, ex-

cept for the WDT time-out reset in the Idle/Sleep Mode, in

which case, the Data Memory bank remains unaffected.

It should be noted that 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. Directly addressing the Data

· BP Register

Bit

76543210

Name

¾¾¾¾¾¾¾

DMBP0

R/W

¾¾¾¾¾¾¾

R/W

POR

¾¾¾¾¾¾¾

Bit 7~1 :

unimplemented, read as

²0²

Bit 0

DMBP0: Data Memory bank point

0: Bank 0

1: Bank 1

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