HT48R05A データシートの表示（PDF） - Holtek Semiconductor

部品番号

コンポーネント説明

一致するリスト

HT48R05A

8-Bit OTP Microcontroller

Holtek Semiconductor 

Preliminary

HT48R05A-1

Functional Description

Execution flow

The system clock for the microcontroller is de-

rived from either a crystal or an RC oscillator.

The system clock is internally divided into four

non-overlapping clocks. One instruction cycle

consists of four system clock cycles.

Instruction fetching and execution are

pipelined in such a way that a fetch takes an in-

struction cycle while decoding and execution

takes the next instruction cycle. However, the

pipelining scheme causes each instruction to ef-

fectively execute in a cycle. If an instruction

changes the program counter, two cycles are re-

quired to complete the instruction.

Program counter - PC

The program counter (PC) controls the se-

quence in which the instructions stored in pro-

gram PROM are executed and its contents

specify full range of program memory.

After accessing a program memory word to fetch

an instruction code, the contents of the program

counter are incremented by one. The program

counter then points to the memory word contain-

ing the next instruction code.

When executing a jump instruction, conditional

skip execution, loading PCL register, subrou-

tine call, initial reset, internal interrupt, exter-

nal interrupt or return from subroutine, the PC

manipulates the program transfer by loading

the address corresponding to each instruction.

The conditional skip is activated by instruc-

tions. Once the condition is met, the next in-

struction, fetched during the current

instruction execution, is discarded and a

dummy cycle replaces it to get the proper in-

struction. Otherwise proceed with the next in-

struction.

The lower byte of the program counter (PCL) is

a readable and writable register (06H). Moving

data into the PCL performs a short jump. The

destination will be within 256 locations.

When a control transfer takes place, an addi-

tional dummy cycle is required.

Program memory - PROM

The program memory is used to store the pro-

gram instructions which are to be executed. It

also contains data, table, and interrupt entries,

and is organized into 512´14 bits, addressed by

the program counter and table pointer.

T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4

S y s te m C lo c k

O S C 2 ( R C o n ly )

PC

PC

PC +1

PC +2

F e tc h IN S T (P C )

E x e c u te IN S T (P C -1 )

F e tc h IN S T (P C + 1 )

E x e c u te IN S T (P C )

Execution flow

F e tc h IN S T (P C + 2 )

E x e c u te IN S T (P C + 1 )

6

February 25, 2000

Share Link: