PIC16LC71-04I/SO Microchip Technology, PIC16LC71-04I/SO Datasheet - Page 61

• Manufacturer Part Number: PIC16LC71-04I/SO
• Description: IC MCU OTP 1KX14 A/D 18SOIC
• Manufacturer: Microchip Technology
• Series: PIC® 16Cr

Specifications of PIC16LC71-04I/SO

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 4MHz
• Peripherals: POR, WDT
• Number Of I /o: 13
• Program Memory Size: 1.75KB (1K x 14)
• Program Memory Type: OTP
• Ram Size: 36 x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 3.6 V
• Data Converters: A/D 4x8b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 18-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Connectivity: -

8.5
The PIC16C71X family has 4 sources of interrupt.
vidual interrupt requests in flag bits. It also has individ-
ual and global interrupt enable bits.
A global interrupt enable bit, GIE (INTCON<7>)
enables (if set) all un-masked 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 be dis-
abled through their corresponding enable bits in vari-
ous 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 inter-
rupt and the TMR0 overflow interrupt flags are con-
tained in the INTCON register.
The peripheral interrupt flags are contained in the spe-
cial function registers PIR1 and PIR2. The correspond-
ing interrupt enable bits are contained in special
function registers PIE1 and PIE2, and the peripheral
interrupt enable bit is contained in special function reg-
ister INTCON.
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.
Applicable Devices
External interrupt RB0/INT
TMR0 overflow interrupt
PORTB change interrupts (pins RB7:RB4)
A/D Interrupt
The interrupt control register (INTCON) records indi-
1997 Microchip Technology Inc.
Note:
Interrupts
Individual interrupt flag bits are set regard-
less of the status of their corresponding
mask bit or the GIE bit.
Interrupt Sources
710 71 711 715
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 (Figure 8-19).
The latency is the same for one or two cycle instruc-
tions. Individual interrupt flag bits are set regardless of
the status of their corresponding mask bit or the GIE
bit.
LOOP BCF
Note:
BTFSC INTCON, GIE
GOTO
:
For the PIC16C71
If an interrupt occurs while the Global Inter-
rupt Enable (GIE) bit is being cleared, the
GIE bit may unintentionally be re-enabled
by the user’s Interrupt Service Routine (the
RETFIE instruction). The events that
would cause this to occur are:
1.
2.
3.
Perform the following to ensure that inter-
rupts are globally disabled:
INTCON, GIE
LOOP
An instruction clears the GIE bit while
an interrupt is acknowledged.
The program branches to the Interrupt
vector and executes the Interrupt Ser-
vice Routine.
The Interrupt Service Routine com-
pletes with the execution of the RET-
FIE instruction. This causes the GIE
bit to be set (enables interrupts), and
the program returns to the instruction
after the one which was meant to dis-
able interrupts.
PIC16C71X
; Disable global
;
; Global interrupt
;
; NO, try again
;
;
;
interrupt bit
disabled?
Yes, continue
with program
flow
DS30272A-page 61