PIC18F4620-I/P Microchip Technology Inc., PIC18F4620-I/P Datasheet - Page 93

• Manufacturer Part Number: PIC18F4620-I/P
• Description: 40 Pin, 64 KB Flash, 3968 RAM, 36 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F4620-I/P

• A/d Inputs: 13-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 1024 Bytes
• Input Output: 36
• Interface: SPI/I2C/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 40-pin PDIP
• Programmable Memory: 64K Bytes
• Ram Size: 4K Bytes
• Speed: 40 MHz
• Timers: 1-8 bit, 3-16 bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

9.0
The PIC18F2525/2620/4525/4620 devices have multi-
ple interrupt sources and an interrupt priority feature
that allows most interrupt sources to be assigned a
high priority level or a low priority level. The high priority
interrupt vector is at 0008h and the low priority interrupt
vector is at 0018h. High priority interrupt events will
interrupt any low priority interrupts that may be in
progress.
There are ten registers which are used to control
interrupt operation. These registers are:
• RCON
• INTCON
• INTCON2
• INTCON3
• PIR1, PIR2
• PIE1, PIE2
• IPR1, IPR2
It is recommended that the Microchip header files
supplied with MPLAB
names in these registers. This allows the assembler/
compiler to automatically take care of the placement of
these bits within the specified register.
In general, interrupt sources have three bits to control
their operation. They are:
• Flag bit to indicate that an interrupt event
• Enable bit that allows program execution to
• Priority bit to select high priority or low priority
The interrupt priority feature is enabled by setting the
IPEN bit (RCON<7>). When interrupt priority is
enabled, there are two bits which enable interrupts
globally. Setting the GIEH bit (INTCON<7>) enables all
interrupts that have the priority bit set (high priority).
Setting the GIEL bit (INTCON<6>) enables all
interrupts that have the priority bit cleared (low priority).
When the interrupt flag, enable bit and appropriate
global interrupt enable bit are set, the interrupt will vec-
tor immediately to address 0008h or 0018h, depending
on the priority bit setting. Individual interrupts can be
disabled through their corresponding enable bits.
 2004 Microchip Technology Inc.
occurred
branch to the interrupt vector address when the
flag bit is set
INTERRUPTS
®
IDE be used for the symbolic bit
PIC18F2525/2620/4525/4620
Preliminary
When the IPEN bit is cleared (default state), the
interrupt priority feature is disabled and interrupts are
compatible with PICmicro
Compatibility mode, the interrupt priority bits for each
source have no effect. INTCON<6> is the PEIE bit,
which enables/disables all peripheral interrupt sources.
INTCON<7> is the GIE bit, which enables/disables all
interrupt sources. All interrupts branch to address
0008h in Compatibility mode.
When an interrupt is responded to, the global interrupt
enable bit is cleared to disable further interrupts. If the
IPEN bit is cleared, this is the GIE bit. If interrupt priority
levels are used, this will be either the GIEH or GIEL bit.
High priority interrupt sources can interrupt a low
priority interrupt. Low priority interrupts are not
processed while high priority interrupts are in progress.
The return address is pushed onto the stack and the
PC is loaded with the interrupt vector address (0008h
or 0018h). Once in the Interrupt Service Routine, the
source(s) of the interrupt can be determined by polling
the interrupt flag bits. The interrupt flag bits must be
cleared in software before re-enabling interrupts to
avoid recursive interrupts.
The “return from interrupt” instruction, RETFIE, exits
the interrupt routine and sets the GIE bit (GIEH or GIEL
if priority levels are used), which re-enables interrupts.
For external interrupt events, such as the INT pins or
the PORTB input change interrupt, the interrupt latency
will be three to four instruction cycles. The exact
latency is the same for one or two-cycle instructions.
Individual interrupt flag bits are set, regardless of the
status of their corresponding enable bit or the GIE bit.
Note:
Do not use the MOVFF instruction to modify
any of the interrupt control registers while
any interrupt is enabled. Doing so may
cause erratic microcontroller behavior.
®
mid-range devices. In
DS39626B-page 91