HT37A70 datasheet(24/85 Pages) HOLTEK

24 / 85 page

HT37A70/60/50/40/30/20

Rev. 1.00

February 17, 2009

RAM1MP2:

MOV

A,RBP2

XOR

A,25

ZERO

; jump to exit loop if rBP2 is

²2²

JMP

RAM2TEST_Exit

MOV

A,60H

; loaded with first RAM address to MP2

MOV

MP2,A

LOOP2:

CLR

WDT

CLR

IAR1

; clear the data at address defined by MP2

SIZ

MP2

; increase MP2, and skip out if MP2 is

²0²

JMP

LOOP2

INC

rBP2

; increase rBP2

JMP

RAM1MP2

RAM2TEST_Exit:

Bank Pointer

- RBP1, RBP2

The RAM Data Memory is divided into 2 Banks, known as

Bank 0 to Bank 1. Selecting the required Data Memory

area is achieved using the RAM Bank Pointers which are

RBP1 and RBP2. The RBP1 and RBP2 match up with

MP1 and MP2 respectively. If data in Bank 0 is to be ac-

cessed, then the RBP registers must be loaded with the

value

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

the RBP registers must be loaded with the value

²01².

Using Memory Pointer MP0 and Indirect Addressing

spective of the value of the Bank Pointer. The RBP1 and

RBP2 register is located at memory location 60H in

Bank 0 to Bank 1 and can only be accessed indirectly

using two memory pointers MP1 and MP2 and the indi-

rect addressing register IAR1 will always access data

from Bank 0 to Bank 1.

The Data Memory is initialized to Bank 0 to Bank 1 after

a reset, except for the WDT time-out reset in the Power

Down Mode, in which case, the Data Memory bank re-

mains unaffected. It should be noted that Special Func-

tion Data Memory is not affected by the bank selection,

which means that the Special Function Registers can be

accessed from within Bank 0 to Bank 1. Directly ad-

dressing the Data Memory will always result in Bank 0

being accessed irrespective of the value of the Bank

Pointer.

Bit No.

Function

RBP1

RAM Bank Point 1 Select

0= Select RAM Bank0

1= Select RAM Bank1

1~7

Unused bit

RBP1 (04H)

Bit No.

Function

RBP2

RAM Bank Point 2 Select

0= Select RAM Bank0

1= Select RAM Bank1

1~7

Unused bit

RBP2 (2FH)

Note: Using MP1 or MP2 are selected by DACC.7.

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.

Look-up Table Registers

- TBLP1, TBMP1, TBHP1,

TBLH

These seven special function registers are used to con-

trol operation of the look-up table which is stored in the

Program Memory. TBLP1, TBMP1 and TBHP1 are the

table pointer and indicate the location where the table

data is located. Their value must be setup before any ta-

ble read commands are executed. Their value can be

changed, for example using the

²INC² or ²DEC² instruc-

tions, allowing for easy table data pointing and reading.

TBLH is the location where the high order byte of the ta-

ble data is stored after a table read data instruction has

been executed. Note that the lower order table data byte

is transferred to a user defined location.

HT37A70 Datasheet(PDF) 24 Page - Holtek Semiconductor Inc

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