PIC16C72 datasheet(72/128 Pages) MICROCHIP

72 / 128 page

PIC16C72 Series

DS39016B-page 72

Preliminary

 1998-2013 Microchip Technology Inc.

Other peripherals cannot generate interrupts since dur-

ing SLEEP, no on-chip clocks are present.

When the SLEEP instruction is being executed, the next

instruction (PC + 1) is pre-fetched. For the device to

wake-up through an interrupt event, the corresponding

interrupt enable bit must be set (enabled). Wake-up is

regardless of the state of the GIE bit. If the GIE bit is

clear (disabled), the device continues execution at the

instruction after the SLEEP instruction. If the GIE bit is

set (enabled), the device executes the instruction after

the SLEEP instruction and then branches to the inter-

rupt address (0004h). In cases where the execution of

the instruction following SLEEP is not desirable, the

user should have a NOP after the SLEEP instruction.

10.13.2 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 com-

plete 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 postscaler 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 instruction

was executed as a NOP.

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

tion should be executed before a SLEEP instruction.

FIGURE 10-14: WAKE-UP FROM SLEEP THROUGH INTERRUPT

10.14

Program Verification/Code Protection

If the code protection bit(s) have not been pro-

grammed, the on-chip program memory can be read

out for verification purposes.

10.15

ID Locations

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

as ID locations where the user can store checksum or

other code-identification numbers. These locations are

not accessible during normal execution but are read-

able and writable during program/verify. It is recom-

mended that only the 4 least significant bits of the ID

location are used.

For ROM devices, these values are submitted along

with the ROM code.

10.16

In-Circuit Serial Programming™

PIC16CXXX family microcontrollers can be serially pro-

grammed 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. This allows customers to manufacture boards

with unprogrammed devices, and then program the

microcontroller just before shipping the product. This

also allows the most recent firmware or a custom firm-

ware to be programmed.

For complete details of serial programming, please

refer to the In-Circuit Serial Programming (ICSP™)

Guide, DS30277.

Q3 Q4

Q1 Q2

Q2 Q3 Q4

Q1 Q2 Q3 Q4

Q2 Q3

Q1 Q2

OSC1

CLKOUT(4)

INT pin

INTF flag

(INTCON<1>)

GIE bit

(INTCON<7>)

INSTRUCTION FLOW

Instruction

fetched

Instruction

executed

PC+1

PC+2

Inst(PC) = SLEEP

Inst(PC - 1)

Inst(PC + 1)

SLEEP

Processor in

SLEEP

Interrupt Latency

(Note 2)

Inst(PC + 2)

Inst(PC + 1)

Inst(0004h)

Inst(0005h)

Inst(0004h)

Dummy cycle

PC + 2

0004h

0005h

Dummy cycle

TOST(2)

PC+2

Note

XT, HS or LP oscillator mode assumed.

TOST = 1024TOSC (drawing not to scale) This delay will not be there for RC osc mode.

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

CLKOUT is not available in these osc modes, but shown here for timing reference.

Note:

Microchip does not recommend code pro-

tecting windowed devices.

PIC16C72 Datasheet(PDF) 72 Page - Microchip Technology

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