HT45F23A View Datasheet(PDF) - Holtek Semiconductor

Part Name

Description

Manufacturer

HT45F23A

8-Bit Flash MCU with Op Amps & Comparators

Holtek Semiconductor 

HT45F23A

8-Bit Flash MCU with Op Amps & Comparators

1

M O V A ,[1 2 H ]

2

C A LL D E LA Y

3

C P L [1 2 H ]

4

:

5

:

6

NOP

D E LA Y :

F e tc h In s t. 1

E x e c u te In s t. 1

F e tc h In s t. 2

E x e c u te In s t. 2

F e tc h In s t. 3

F lu s h P ip e lin e

F e tc h In s t. 6

E x e c u te In s t. 6

F e tc h In s t. 7

Instruction Fetching

Program Counter

During program execution, the Program Counter is used to keep track of the address of the next

instruction to be executed. It is automatically incremented by one each time an instruction is

executed except for instructions, such as "JMP" or "CALL" that demand a jump to a non-consecutive

Program Memory address. Note that the Program Counter width varies with the Program Memory

capacity depending upon which device is selected. However, it must be noted that only the lower

8 bits, known as the Program Counter Low Register, are directly addressable by the application

program.

When executing instructions requiring jumps to non-consecutive addresses such as a jump

instruction, a subroutine call, interrupt or reset, etc., the microcontroller manages program control

by loading the required address into the Program Counter. For conditional skip instructions, once

the condition has been met, the next instruction, which has already been fetched during the present

instruction execution, is discarded and a dummy cycle takes its place while the correct instruction is

obtained.

Program Counter

Program Counter High Byte

PCL Register

PC10~PC8

PCL7~PCL0

The lower byte of the Program Counter, known as the Program Counter Low register or PCL, is

available for program control and is a readable and writeable register. By transferring data directly

into this register, a short program jump can be executed directly. However, as only this low byte

is available for manipulation, the jumps are limited to the present page of memory that is 256

locations. When such program jumps are executed, it should also be noted that a dummy cycle will

be inserted.

The lower byte of the Program Counter is fully accessible under program control. Manipulating the

PCL might cause program branching, so an extra cycle is needed to pre-fetch. Further information

on the PCL register can be found in the Special Function Register section.

Rev. 1.00

21

July 03, 2012

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