HTG13J0 データシートの表示（PDF） - Holtek Semiconductor

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HTG13J0

4-Bit Microcontroller

Holtek Semiconductor 

In the execution of an instruction, the program

counter is added before the executing phase. So

a careful manipulation of READ MR0A and

READ R4A is needed in the page margin.

Stack register

The stack register is a group of registers used to

save the contents of the program counter (PC)

and is arranged in 13 bits ´ 1 level. One bit is

used to store the carry flag. An interrupt will

force the contents of the PC and the carry flag

onto the stack register. A subroutine call will

also cause the PC contents to be pushed onto

the stack; however the carry flag will not be

stored. At the end of a subroutine or an inter-

rupt (indicated by a return instruction RET or

RETI), the contents of the stack register are re-

turned to the PC.

Executing "RETI" instruction will restore the

carry flag from the stack register, but "RET"

does not.

Working registers - R0,R1,R2,R3,R4

These five registers are usually used to store

the frequently accessed data. The working reg-

ister can be incremented (+1) or decremented

(-1). The JNZ Rn, address (n=0,1,4) instruction

makes efficient use of the working register as a

program loop counter. Also the register pairs of

R1, R0 and R3, R2 can be used as the data mem-

ory pointer, when the data memory transfer in-

struction is executed.

Data memory - RAM

The data memory is a static RAM organized

with 256 ´ 4 bit format and is used to store tem-

porary data and display data. All of the data

memory locations are indirectly addressable through

the register pair "R1,R0" or "R3,R2".

There are two areas in the data memory, tempo-

rary data area and display data area. Access to

the temporary data memory is made through

00H-9FH address, and access to the display

data memory is made through B0H-FFH ad-

dress.

The locations between the temporary and display

data areas are undefined and cannot be used.

HT13J0

00H

Temporary Data Area

(160 x 4)

A0H

Undefined Area

B0H

Display Data Area

(80 x 4)

FFH

4 bits

Data memory

Data RAM

When data is written in the display area, the

LCD driver automatically reads it and

gene-rates an LCD driving signal.

Accumulator - ACC

The register ACC plays the most important role

in data manipulation and data transfer. It is

not only one of the sources of input to the ALU

but also the destination of the result due to

ALU. Data transfer can be performed between

ACC and other registers, data memory or I/O

ports.

Arithmetic and logic unit - ALU

This circuit performs arithmetic and logic oper-

ation. The ALU provides the following func-

tions:

Arithmetic operation (ADD, ADC, SUB, SBC,

DAA)

· Logic operation (AND, OR, XOR)

· Rotation (RL, RR, RLC, RRC)

· Increment and Decrement (INC, DEC)

· Branch decision (JZ, JNZ, JC, JNC...)

· The ALU not only outputs the results of data

operation but also sets the status of carry flag

(C) in some instructions.

Timer

This is a programmable 8-bit count-up counter

internal frequency sources to aid the user in

counting and generate accurate time base.

10

May 19, 1999

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