PIC18C858-E/L Microchip Technology, PIC18C858-E/L Datasheet - Page 44

• Manufacturer Part Number: PIC18C858-E/L
• Description: IC MCU OTP 16KX16 CAN 84PLCC
• Manufacturer: Microchip Technology
• Series: PIC® 18Cr

Specifications of PIC18C858-E/L

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: CAN, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LVD, POR, PWM, WDT
• Number Of I /o: 68
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: OTP
• Ram Size: 1.5K x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 16x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 84-PLCC
• For Use With: AC164310 - MODULE SKT FOR PM3 84PLCCDVA18XL840 - ADAPTER DEVICE ICE 84PLCCAC174012 - MODULE SKT PROMATEII 84PLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Other names: PIC18C858E/L

PIC18CXX8
4.2.3
Since the Top-of-Stack (TOS) is readable and writable,
the ability to push values onto the stack and pull values
off the stack without disturbing normal program execu-
tion is a desirable option. To push the current PC value
onto the stack, a PUSH instruction can be executed.
This will increment the stack pointer and load the cur-
rent PC value onto the stack. TOSU, TOSH and TOSL
can then be modified to place a return address on the
stack.
The POP instruction discards the current TOS by decre-
menting the stack pointer. The previous value pushed
onto the stack then becomes the TOS value.
4.2.4
These RESETs are enabled by programming the
STVREN configuration bit. When the STVREN bit is
disabled, a full or underflow condition will set the appro-
priate STKFUL or STKUNF bit, but not cause a device
RESET. When the STVREN bit is enabled, a full or
underflow will set the appropriate STKFUL or STKUNF
bit and then cause a device RESET. The STKFUL or
STKUNF bits are only cleared by the user software or
a POR.
DS30475A-page 44
PUSH AND POP INSTRUCTIONS
STACK FULL/UNDERFLOW RESETS
Advanced Information
4.3
A “fast return” option is available for interrupts and
calls. A fast register stack is provided for the STATUS,
WREG and BSR registers and is only one layer in
depth. The stack is not readable or writable and is
loaded with the current value of the corresponding reg-
ister when the processor vectors for an interrupt. The
values in the fast register stack are then loaded back
into the working registers if the fast return instruc-
tion is used to return from the interrupt.
A low or high priority interrupt source will push values
into the stack registers. If both low and high priority
interrupts are enabled, the stack registers cannot be
used reliably for low priority interrupts. If a high priority
interrupt occurs while servicing a low priority interrupt,
the stack register values stored by the low priority inter-
rupt will be overwritten.
If high priority interrupts are not disabled during low pri-
ority interrupts, users must save the key registers in
software during a low priority 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 fast call instruction
must be executed.
Example 4-1 shows a source code example that uses
the fast register stack.
EXAMPLE 4-1:
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
 2000 Microchip Technology Inc.