16C84 datasheet(49/110 Pages) MICROCHIP

49 / 110 page

PIC16C84

 1996-2013 Microchip Technology Inc.

DS30445D-page 49

8.12.3

WAKE-UP USING INTERRUPTS

When global interrupts are disabled (GIE cleared) and

any interrupt source has both its interrupt enable bit

and interrupt flag bit set, one of the following will occur:

• If the interrupt occurs before the execution of a

SLEEP instruction, the SLEEP instruction will

complete as a NOP. Therefore, the WDT and

WDT postscaler will not be cleared, the TO bit will

not be set and PD bits will not be cleared.

• If the interrupt occurs during or after the execu-

tion of a SLEEP instruction, the device will imme-

diately wake up from sleep . The SLEEP

instruction will be completely executed before the

wake-up. Therefore, the WDT and WDT post-

scaler will be cleared, the TO bit will be set and

the PD bit will be cleared.

Even if the flag bits were checked before executing a

SLEEP instruction, it may be possible for flag bits to

become set before the SLEEP instruction completes.

To determine whether a SLEEP instruction executed,

test the PD bit. If the PD bit is set, the SLEEP instruc-

tion was executed as a NOP.

To ensure that the WDT is cleared, a CLRWDT instruc-

tion should be executed before a SLEEP instruction.

8.13

Program Verification/Code Protection

the

code

protection

bit(s)

have

not

been

programmed, the on-chip program memory can be

read out for verification purposes.

8.14

ID Locations

Four memory locations (2000h - 2003h) are designated

as ID locations to store checksum or other code

identification

numbers.

These

locations

are

not

accessible during normal execution but are readable

and writable only during program/verify. Only the

4 least significant bits of ID location are usable.

For ROM devices, these values are submitted along

with the ROM code.

8.15

In-Circuit Serial Programming

PIC16C84

microcontrollers

can

serially

programmed while in the end application circuit. This is

simply done with two lines for clock and data, and three

other lines for power, ground, and the programming

voltage. Customers can manufacture boards with

unprogrammed

devices,

and

then

program

the

microcontroller just before shipping the product,

allowing the most recent firmware or custom firmware

to be programmed.

The device is placed into a program/verify mode by

holding the RB6 and RB7 pins low, while raising the

MCLR pin from VIL to VIHH (see

PIC16C84 EEPROM

Memory Programming Specification (DS30189)). RB6

becomes the programming clock and RB7 becomes

the programming data. Both RB6 and RB7 are Schmitt

Trigger inputs in this mode.

After reset, to place the device into programming/verify

mode, the program counter (PC) points to location 00h.

A 6-bit command is then supplied to the device, 14-bits

of program data is then supplied to or from the device,

using load or read-type instructions. For complete

details of serial programming, please refer to the

In-Cir-

cuit Serial Programming Guide (DS30277).

For ROM devices, both the program memory and Data

EEPROM memory may be read, but only the Data

EEPROM memory may be programmed.

FIGURE 8-19: TYPICAL IN-SYSTEM SERIAL

PROGRAMMING

CONNECTION

Note:

Microchip does not recommend code pro-

tecting windowed devices..

External

Connector

Signals

To Normal

Connections

To Normal

Connections

PIC16CXX

VDD

VSS

MCLR/VPP

RB6

RB7

+5V

VPP

CLK

Data I/O

VDD

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