PIC16LC712 datasheet(61/106 Pages) MICROCHIP

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DS41106C-page 61

PIC16C712/716

9.10

Interrupts

The PIC16C712/716 devices have up to 7 sources of

interrupt. The Interrupt Control Register (INTCON)

records individual interrupt requests in flag bits. It also

has individual and global interrupt enable bits.

A Global Interrupt Enable bit, GIE (INTCON<7>)

enables (if set) all unmasked interrupts or disables (if

cleared) all interrupts. When bit GIE is enabled, and an

interrupt’s flag bit and mask bit are set, the interrupt will

vector

immediately. Individual

interrupts

can

disabled through their corresponding enable bits in

various registers. Individual interrupt bits are set,

regardless of the status of the GIE bit. The GIE bit is

cleared on Reset.

The “return from interrupt” instruction, RETFIE, exits

the interrupt routine, as well as sets the GIE bit, which

re-enables interrupts.

The RB0/INT pin interrupt, the RB port change interrupt

and the TMR0 overflow interrupt flags are contained in

the INTCON register.

The peripheral interrupt flags are contained in the

Special Function Registers, PIR1 and PIR2. The corre-

sponding interrupt enable bits are contained in Special

Function Registers, PIE1 and PIE2, and the peripheral

interrupt enable bit is contained in Special Function

When an interrupt is responded to, the GIE bit is

cleared to disable any further interrupt, the return

address is pushed onto the stack and the PC is loaded

with 0004h. Once in the Interrupt Service Routine, the

source(s) of the interrupt can be determined by polling

the interrupt flag bits. The interrupt flag bit(s) must be

cleared in software before re-enabling interrupts to

avoid recursive interrupts.

For external interrupt events, such as the INT pin or

PORTB change interrupt, the interrupt latency will be

three or four instruction cycles. The exact latency

depends when the interrupt event occurs. The latency

is the same for one or two cycle instructions. Individual

interrupt flag bits are set, regardless of the status of

their corresponding mask bit or the GIE bit.

FIGURE 9-14:

INTERRUPT LOGIC

Note:

Individual interrupt flag bits are set regard-

less of the status of their corresponding

mask bit or the GIE bit.

ADIF

ADIE

CCP1IF

CCP1IE

TMR2IF

TMR2IE

TMR1IF

TMR1IE

T0IF

T0IE

INTF

INTE

RBIF

RBIE

GIE

PEIE

Wake-up (If in Sleep mode)

Interrupt to CPU

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