PIC18F8527-I View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC18F8527-I

64/80-Pin, 1-Mbit, Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

Microchip Technology 

PIC18F8722 FAMILY

5.2.3

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). To maintain alignment

with instruction boundaries, the PC increments in steps

of 2 and the LSb will always read ‘0’ (see Section 5.1.2

“Program Counter”).

Figure 5-5 shows an example of how instruction words

are stored in the program memory.

The CALL and GOTO instructions have the 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 5-5 shows how the

instruction GOTO 0006h 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 represents the

number of single-word instructions that the PC will be

offset by. Section 26.0 “Instruction Set Summary”

provides further details of the instruction set.

FIGURE 5-5:

INSTRUCTIONS IN PROGRAM MEMORY

Program Memory

Byte Locations →

LSB = 1

LSB = 0

Instruction 1: MOVLW

055h

0Fh

55h

Instruction 2: GOTO

0006h

EFh

03h

F0h

00h

Instruction 3: MOVFF

123h, 456h

C1h

23h

F4h

56h

Word Address

↓

000000h

000002h

000004h

000006h

000008h

00000Ah

00000Ch

00000Eh

000010h

000012h

000014h

DS39646B-page 70

Preliminary

 2004 Microchip Technology Inc.

Share Link: