PIC18C658-I/L Microchip Technology, PIC18C658-I/L Datasheet - Page 42

• Manufacturer Part Number: PIC18C658-I/L
• Description: IC PIC MCU OTP 16KX16 68PLCC
• Manufacturer: Microchip Technology
• Series: PIC® 18Cr

Specifications of PIC18C658-I/L

• Core Size: 8-Bit
• Program Memory Size: 32KB (16K x 16)
• Peripherals: Brown-out Detect/Reset, LVD, POR, PWM, WDT
• Core Processor: PIC
• Speed: 40MHz
• Connectivity: CAN, I²C, SPI, UART/USART
• Number Of I /o: 52
• Program Memory Type: OTP
• Ram Size: 1.5K x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 12x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 68-PLCC
• Controller Family/series: PIC18
• No. Of I/o's: 52
• Ram Memory Size: 1.5KB
• Cpu Speed: 40MHz
• No. Of Timers: 4
• Processor Series: PIC18C
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 1536 B
• Interface Type: 3-Wire, I2C, SPI, USART, CAN
• Maximum Clock Frequency: 40 MHz
• Number Of Programmable I/os: 52
• Number Of Timers: 4 bit
• Operating Supply Voltage: 2.5 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: ICE2000, DM163007, DV164136
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 6
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AC164308 - MODULE SKT FOR PM3 68PLCCDVA18PQ640 - DEVICE ADAPT PIC18C658 64-TQFPAC174007 - MODULE SKT PROMATEII 68PLCC
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details
• Other names: PIC18C658IL; Q1162292

PIC18CXX8
4.2
The return address stack allows any combination of up
to 31 program calls and interrupts to occur. The PC
(Program Counter) is pushed onto the stack when a
PUSH, CALL or RCALL instruction is executed, or an
interrupt is acknowledged. The PC value is pulled off
the stack on a RETURN, RETLW or a RETFIE instruc-
tion. PCLATU and PCLATH are not affected by any of
the return instructions.
The stack operates as a 31 word by 21-bit stack mem-
ory and a 5-bit stack pointer, with the stack pointer ini-
tialized to 00000b after all RESETs. There is no RAM
associated with stack pointer 00000b. This is only a
RESET value. During a CALL type instruction causing
a push onto the stack, the stack pointer is first incre-
mented and the RAM location pointed to by the stack
pointer is written with the contents of the PC. During a
RETURN type instruction causing a pop from the stack,
the contents of the RAM location indicated by the
STKPTR is transferred to the PC and then the stack
pointer is decremented.
The stack space is not part of either program or data
space. The stack pointer is readable and writable, and
the data on the top of the stack is readable and writable
through SFR registers. Status bits indicate if the stack
pointer is at or beyond the 31 levels provided.
4.2.1
The top of the stack is readable and writable. Three
register locations, TOSU, TOSH and TOSL allow
access to the contents of the stack location indicated
by the STKPTR register. This allows users to imple-
ment a software stack if necessary. After a CALL,
RCALL or interrupt, the software can read the pushed
value by reading the TOSU, TOSH and TOSL registers.
These values can be placed on a user defined software
stack. At return time, the software can replace the
TOSU, TOSH and TOSL and do a return.
The user should disable the global interrupt enable bits
during this time to prevent inadvertent stack opera-
tions.
DS30475A-page 42
Return Address Stack
TOP-OF-STACK ACCESS
Advanced Information
4.2.2
The STKPTR register contains the stack pointer value,
the STKFUL (stack full) status bit, and the STKUNF
(stack underflow) status bits. Register 4-1 shows the
STKPTR register. The value of the stack pointer can be
0 through 31. The stack pointer increments when val-
ues are pushed onto the stack and decrements when
values are popped off the stack. At RESET, the stack
pointer value will be 0. The user may read and write the
stack pointer value. This feature can be used by a Real
Time Operating System for return stack maintenance.
After the PC is pushed onto the stack 31 times (without
popping any values off the stack), the STKFUL bit is
set. The STKFUL bit can only be cleared in software or
by a POR.
The action that takes place when the stack becomes
full depends on the state of the STVREN (stack over-
flow RESET enable) configuration bit. Refer to Section
18 for a description of the device configuration bits. If
STVREN is set (default) the 31st push will push the
(PC + 2) value onto the stack, set the STKFUL bit, and
reset the device. The STKFUL bit will remain set and
the stack pointer will be set to 0.
If STVREN is cleared, the STKFUL bit will be set on the
31st push and the stack pointer will increment to 31.
The 32nd push will overwrite the 31st push (and so on),
while STKPTR remains at 31.
When the stack has been popped enough times to
unload the stack, the next pop will return a value of zero
to the PC and sets the STKUNF bit, while the stack
pointer remains at 0. The STKUNF bit will remain set
until cleared in software or a POR occurs.
Note:
RETURN STACK POINTER (STKPTR)
Returning a value of zero to the PC on an
underflow has the effect of vectoring the
program to the RESET vector, where the
stack conditions can be verified and appro-
priate actions can be taken.
 2000 Microchip Technology Inc.