PIC18F4539-ESLASHMLSQTP datasheet(208/322 Pages) MICROCHIP

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PIC18FXX39

DS30485A-page 206

Preliminary

 2002 Microchip Technology Inc.

FIGURE 20-2:

WAKE-UP FROM SLEEP THROUGH INTERRUPT(1,2)

20.4

Program Verification and

Code Protection

The overall structure of the code protection on the

PIC18 FLASH devices differs significantly from other

PICmicro devices. The user program memory is

divided on binary boundaries into individual blocks,

each of which has three separate code protection bits

associated with it:

• Code Protect bit (CPn)

• Write Protect bit (WRTn)

• External Block Table Read bit (EBTRn)

The code protection bits are located in Configuration

Registers 5L through 7H. Their locations within the

registers are summarized in Table 20-3.

In the PIC18FXX39 family, program memory is divided

into segments of 8 Kbytes. The first block in turn

divided into a boot block of 512 bytes and a separately

protected remainder (Block 0) of 7.5 Kbytes. This

means for PIC18FXX39 devices, that there may be up

to five blocks, depending on the program memory size.

The organization of the blocks and their associated

code protection bits are shown in Figure 20-3.

For PIC18FX439 devices, program memory is divided

into three blocks: a boot block, Block 0 (7.5 Kbytes)

and Block 1 (8 Kbytes). Block 1 is further divided in

half; the upper portion above 3000h is reserved, and

unavailable to user applications. The entire block can

be protected as a whole by bits CP1, WRT1 and

EBTR1. By default, Block 1 is not code protected.

For PIC18FX539 devices, program memory is divided

into five blocks: the boot block, Block 0 (7.5 Kbytes),

and Blocks 1 through 3 (8 Kbytes). Code protection is

implemented for the boot block and Blocks 0 through 2.

There is no provision for code protection for Block 3.

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

OSC1

CLKO(4)

INT pin

INTF Flag

(INTCON<1>)

GIEH bit

(INTCON<7>)

INSTRUCTION FLOW

Instruction

Fetched

Instruction

Executed

PC+2

PC+4

Inst(PC) = SLEEP

Inst(PC - 1)

Inst(PC + 2)

SLEEP

Processor in

SLEEP

Interrupt Latency(3)

Inst(PC + 4)

Inst(PC + 2)

Inst(0008h)

Inst(000Ah)

Inst(0008h)

Dummy Cycle

PC + 4

0008h

000Ah

Dummy Cycle

TOST(2)

PC+4

Note

XT, HS or LP Oscillator mode assumed.

GIE = 1 assumed. In this case, after wake-up, the processor jumps to the interrupt routine. If GIE = 0, execution will continue in-line.

TOST = 1024 TOSC (drawing not to scale). This delay will not occur for RC and EC Osc modes.

CLKO is not available in these Osc modes, but shown here for timing reference.

Note:

The reserved segments of the program

memory space are used by the Motor Con-

trol kernel. For the kernel to function prop-

erly, this area must not be write protected.

If users are developing applications that

require code protection for PIC18FX439

devices, they should restrict program code

(or at least those sections requiring protec-

tion) to below the 1FFFh memory

boundary.

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