PIC17C756-16/L Microchip Technology, PIC17C756-16/L Datasheet - Page 50

• Manufacturer Part Number: PIC17C756-16/L
• Description: MICRO CTRL 16K MEMORY OTP 68PLCC
• Manufacturer: Microchip Technology
• Series: PIC® 17Cr

Specifications of PIC17C756-16/L

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 50
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: OTP
• Ram Size: 902 x 8
• Voltage - Supply (vcc/vdd): 4 V ~ 6 V
• Data Converters: A/D 12x10b
• Oscillator Type: External
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 68-PLCC
• For Use With: AC164308 - MODULE SKT FOR PM3 68PLCCDVA17XL681 - DEVICE ADAPTER FOR PIC17C752DM173001 - KIT DEVELOPMENT PICDEM17AC174007 - MODULE SKT PROMATEII 68PLCCAC164024 - ADAPTER PICSTART PLUS 68PLCC
• Lead Free Status / RoHS Status: Request inventory verification / Request inventory verification
• Eeprom Size: -

7.3
PIC17C75X devices have a 16 x 16-bit hardware stack
(Figure 7-1). The stack is not part of either the program
or data memory space, and the stack pointer is neither
readable nor writable. The PC (Program Counter) is
“PUSHed” onto the stack when a CALL or LCALL
instruction is executed or an interrupt is acknowledged.
The stack is “POPed” in the event of a RETURN, RETLW,
or a RETFIE instruction execution. PCLATH is not
affected by a “PUSH” or a “POP” operation.
The stack operates as a circular buffer, with the stack
pointer initialized to '0' after all resets. There is a stack
available bit (STKAV) to allow software to ensure that
the stack has not overflowed. The STKAV bit is set
after a device reset. When the stack pointer equals Fh,
STKAV is cleared. When the stack pointer rolls over
from Fh to 0h, the STKAV bit will be held clear until a
device reset.
After the device is “PUSHed” sixteen times (without a
“POP”), the seventeenth push overwrites the value
from the first push. The eighteenth push overwrites the
second push (and so on).
DS30264A-page 50
Note 1: There is not a status bit for stack under-
Note 2: There are no instruction mnemonics
Note 3: After a reset, if a “POP” operation occurs
Stack Operation
flow. The STKAV bit can be used to detect
the underflow which results in the stack
pointer being at the top of stack.
called PUSH or POP. These are actions
that occur from the execution of the CALL,
RETURN, RETLW, and RETFIE instruc-
tions, or the vectoring to an interrupt vec-
tor.
before a “PUSH” operation, the STKAV bit
will be cleared. This will appear as if the
stack is full (underflow has occurred). If a
“PUSH” operation occurs next (before
another “POP”), the STKAV bit will be
locked clear. Only a device reset will
cause this bit to set.
Preliminary
7.4
Indirect addressing is a mode of addressing data
memory where the data memory address in the
instruction is not fixed. That is, the register that is to be
read or written can be modified by the program. This
can be useful for data tables in the data memory.
Figure 7-9 shows the operation of indirect addressing.
This shows the moving of the value to the data mem-
ory address specified by the value of the FSR register.
Example 7-1 shows the use of indirect addressing to
clear RAM in a minimum number of instructions. A
similar concept could be used to move a defined num-
ber of bytes (block) of data to the USART transmit reg-
ister (TXREG). The starting address of the block of
data to be transmitted could easily be modified by the
program.
FIGURE 7-9:
Instruction
Executed
Instruction
Fetched
Indirect Addressing
Opcode
Opcode
INDIRECT ADDRESSING
Address
File
1997 Microchip Technology Inc.
File = INDFx
FSR
RAM