PIC16F54-ESLASHP datasheet(41/88 Pages) MICROCHIP

41 / 88 page

DS41213D-page 39

PIC16F5X

8.3

Power-Down Mode (Sleep)

A device may be powered down (Sleep) and later

powered up (wake-up from Sleep).

8.3.1

SLEEP

The Power-down mode is entered by executing a

SLEEP

instruction.

If enabled, the Watchdog Timer will be cleared but

keeps running, the TO bit (STATUS<4>) is set, the PD

bit (STATUS<3>) is cleared and the oscillator driver is

turned off. The I/O ports maintain the status they had

before the SLEEP instruction was executed (driving

high, driving low or high-impedance).

It should be noted that a Reset generated by a WDT

time-out does not drive the MCLR/VPP pin low.

For lowest current consumption while powered down,

the T0CKI input should be at VDD or VSS and the

MCLR/VPP pin must be at a logic high level

(MCLR = VIH).

8.3.2

WAKE-UP FROM SLEEP

The device can wake-up from Sleep through one of the

following events:

An external Reset input on MCLR/VPP pin.

A Watchdog Timer time-out Reset (if WDT was

enabled).

Both of these events cause a device Reset. The TO

and PD bits can be used to determine the cause of

device Reset. The TO bit is cleared if a WDT time-out

occurred (and caused wake-up). The PD bit, which is

set on power-up, is cleared when SLEEP is invoked.

The WDT is cleared when the device wakes from

Sleep, regardless of the wake-up source.

8.4

Program Verification/Code

Protection

If the code protection bit has not been programmed, the

on-chip program memory can be read out for

verification purposes.

Once code protection is enabled, all program memory

locations above 0x3F read all ‘0’s. Program memory

locations 0x00-0x3F are always unprotected. The user

ID locations and the Configuration Word read out in an

unprotected fashion. It is possible to program the user

ID locations and the Configuration Word after code

protect is enabled.

8.5

User ID Locations

Four memory locations are designated as user ID loca-

tions where the user can store checksum or other

code-identification numbers. These locations are not

accessible during normal execution, but are readable

and writable during Program/Verify.

Use only the lower 4 bits of the user ID locations and

always program the upper 8 bits as ‘1’s.

8.6

In-Circuit Serial Programming™

(ICSP™)

The

PIC16F5X

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 programming

voltage. This allows customers to manufacture boards

with unprogrammed devices and then program the

microcontroller just before shipping the product. Thus,

the most recent firmware or custom firmware can be

programmed.

The device is placed into a Program/Verify mode by

holding the RB6 and RB7 pins low while raising the

MCLR (VPP) pin from VIL to VIHH (see programming

specification). RB6 becomes the programming clock

and RB7 becomes the programming data. Both RB6

and RB7 are Schmitt Trigger inputs in this mode.

A 6-bit command is then supplied to the device.

Depending on the command, 14 bits of program data

are then supplied to or from the device, depending if

the command was a Load or a Read. For complete

details of serial programming, please refer to the

respective Programming Specifications: “PIC16F54

Memory

Programming

Specification”

(DS41207),

“PIC16F57

Memory

Programming

Specification”

(DS41208), and “PIC16F59 Memory Programming

Specification” (DS41243).

A typical In-Circuit Serial Programming connection is

shown in Figure 8-1.

Note:

Microchip will assign a unique pattern

number for QTP and SQTP requests. This

pattern number will be unique and trace-

able to the submitted code.

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