PIC18F010T-I/SN 查看數據表（PDF） - Microchip Technology

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PIC18F010T-I/SN

High Performance Microcontrollers

Microchip Technology 

PIC18F010/020

4.7 Instructions in Program Memory

The program memory is addressed in bytes. Instruc-

tions are stored as two bytes or four bytes in program

memory. The least significant byte of an instruction

word is always stored in a program memory location

with an even address (LSB = ’0’). Figure 4-5 shows an

example of how instruction words are stored in the pro-

gram memory. To maintain alignment with instruction

boundaries, the PC increments in steps of 2 and the

LSB will always read ’0’ (see Section 4.4).

The CALL and GOTO instructions have an absolute pro-

gram memory address embedded into the instruction.

Since instructions are always stored on word bound-

aries, the data contained in the instruction is a word

address. The word address is written to PC<20:1>,

which accesses the desired byte address in program

memory. Instruction #2 in Figure 4-5 shows how the

instruction "GOTO 000006h’ is encoded in the program

memory. Program branch instructions, which encode a

relative address offset, operate in the same manner.

The offset value stored in a branch instruction repre-

sents the number of single word instructions that the

PC will be offset by. Section 13.0 provides further

details of the instruction set.

FIGURE 4-5:

INSTRUCTIONS IN PROGRAM MEMORY

Program Memory

Byte Locations

→

LSB = 1

Instruction 1: MOVLW

055h

0Fh

Instruction 2: GOTO

000006h

EFh

F0h

Instruction 3: MOVFF

123h, 456h

C1h

F4h

LSB = 0

55h

03h

00h

23h

56h

Word Address

↓

000000h

000002h

000004h

000006h

000008h

00000Ah

00000Ch

00000Eh

000010h

000012h

000014h

 2001 Microchip Technology Inc.

Preliminary

DS41142A-page 29

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