HT46R0664 datasheet(14/92 Pages) HOLTEK

14 / 92 page

Rev. 1.00

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Rev. 1.00

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HT46R0664

Enhanced A/D+LCD Type 8-Bit OTP MCU

Fe tc h In s t. (P C)

Ex ec ut e In s t. ( PC -1 )

Fe tc h In s t. ( PC +1 )

Ex ec ut e In st . (P C)

Fe tc h In s t. (P C+ 2)

Ex ec ut e In st . ( PC +1 )

PC +1

PC +2

f SY S

(S ys te m Cl o ck)

Ph as e Cl o ck T1

Pr ogr am C ount er

Ph as e Cl o ck T2

Ph as e Cl o ck T3

Ph as e Cl o ck T4

Pi pe li ni ng

System Clocking and Pipelining

Fe tc h In st . 1E xe cu te In s t. 1

Fe tc h In s t. 2

Fl us h Pi pe lin e

6 DE L AY:

MO V A, [1 2H ]

CA LL D EL AY

CP L [ 12H ]

NO P

Ex ec ut e In st . 2

Fe tc h In s t. 3

Fe tc h In s t. 6

Ex ec ut e In st . 6

Fe tc h In st . 7

Instruction Fetching

Program Counter – PC

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. It must be noted that only the lower 8 bits, known as the

Program Counter Low Register, are directly addressable by user.

When executing instructions requiring jumping 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

Hi�h Byte of Por�ram

Low Byte of Por�ram

PC11~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 in the present page of memory, which have

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.

HT46R0664 Datasheet(PDF) 14 Page - Holtek Semiconductor Inc

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