PIC18F1320-I/SO Microchip Technology, PIC18F1320-I/SO Datasheet - Page 46

• Manufacturer Part Number: PIC18F1320-I/SO
• Description: IC MCU FLASH 4KX16 A/D 18SOIC
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F1320-I/SO

• Program Memory Type: FLASH
• Program Memory Size: 8KB (4K x 16)
• Package / Case: 18-SOIC (7.5mm Width)
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: UART/USART
• Peripherals: Brown-out Detect/Reset, LVD, POR, PWM, WDT
• Number Of I /o: 16
• Eeprom Size: 256 x 8
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 7x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Processor Series: PIC18F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Interface Type: EUSART
• Maximum Clock Frequency: 40 MHz
• Number Of Programmable I/os: 16
• Number Of Timers: 4
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734, 52712-325, EWPIC18
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, ICE4000, DM163014, DV164136
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 7-ch x 10-bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: DVA12XP080 - ADAPTER DEVICE FOR MPLAB-ICEAC164010 - MODULE SKT PROMATEII DIP/SOIC
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PIC18F1220/1320
5.3
A “fast return” option is available for interrupts. A fast
register stack is provided for the Status, WREG and
BSR registers and is only one in depth. The stack is not
readable or writable and is loaded with the current
value of the corresponding register when the processor
vectors for an interrupt. The values in the registers are
then loaded back into the working registers, if the
RETFIE, FAST instruction is used to return from the
interrupt.
All interrupt sources will push values into the stack
registers. If both low and high priority interrupts are
enabled, the stack registers cannot be used reliably to
return from low priority interrupts. If a high priority inter-
rupt occurs while servicing a low priority interrupt, the
stack register values stored by the low priority interrupt
will be overwritten. Users must save the key registers
in software during a low priority interrupt.
If interrupt priority is not used, all interrupts may use the
fast register stack for returns from interrupt.
If no interrupts are used, the fast register stack can be
used to restore the Status, WREG and BSR registers at
the end of a subroutine call. To use the fast register
stack for a subroutine call, a CALL LABEL, FAST
instruction must be executed to save the Status,
WREG and BSR registers to the fast register stack. A
RETURN, FAST instruction is then executed to restore
these registers from the fast register stack.
Example 5-1 shows a source code example that uses
the fast register stack during a subroutine call and
return.
EXAMPLE 5-1:
DS39605C-page 44
CALL SUB1, FAST
SUB1
RETURN, FAST
Fast Register Stack
FAST REGISTER STACK
CODE EXAMPLE
;STATUS, WREG, BSR
;SAVED IN FAST REGISTER
;STACK
;RESTORE VALUES SAVED
;IN FAST REGISTER STACK
5.4
The Program Counter (PC) specifies the address of the
instruction to fetch for execution. The PC is 21-bits
wide. The low byte, known as the PCL register, is both
readable and writable. The high byte, or PCH register,
contains the PC<15:8> bits and is not directly readable
or writable. Updates to the PCH register may be per-
formed through the PCLATH register. The upper byte is
called PCU. This register contains the PC<20:16> bits
and is not directly readable or writable. Updates to the
PCU register may be performed through the PCLATU
register.
The contents of PCLATH and PCLATU will be
transferred to the program counter by any operation
that writes PCL. Similarly, the upper two bytes of the
program counter will be transferred to PCLATH and
PCLATU by an operation that reads PCL. This is useful
for computed offsets to the PC (see Section 5.8.1
“Computed GOTO”).
The PC addresses bytes in the program memory. To
prevent the PC from becoming misaligned with word
instructions, the LSB of PCL is fixed to a value of ‘0’.
The PC increments by 2 to address sequential
instructions in the program memory.
The CALL, RCALL, GOTO and program branch instruc-
tions write to the program counter directly. For these
instructions, the contents of PCLATH and PCLATU are
not transferred to the program counter.
PCL, PCLATH and PCLATU
 2004 Microchip Technology Inc.