PIC16F1947-I/PT Microchip Technology Inc., PIC16F1947-I/PT Datasheet - Page 49

• Manufacturer Part Number: PIC16F1947-I/PT
• Description: 64 TQFP 10x10x1mm TRAY28KB Flash, 1KB RAM, 256B EEPROM, LCD, 1.8-5.5V
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F1947-I/PT

• A/d Inputs: 17-Channel, 10-Bit
• Comparators: 3
• Cpu Speed: 8 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 54
• Interface: CAN/I2C/SPI/UART/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 64-pin TQFP
• Programmable Memory: 28K Bytes
• Ram Size: 1K Bytes
• Speed: 32 MHz
• Timers: 4-8-bit, 1-16-bit
• Voltage, Range: 1.8-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

3.4
All devices have a 16-level x 15-bit wide hardware
stack (refer to Figures
not part of either program or data space. The PC is
PUSHed onto the stack when CALL or CALLW instruc-
tions are executed or an interrupt causes a branch. The
stack is POPed in the event of a RETURN, RETLW or a
RETFIE instruction execution. PCLATH is not affected
by a PUSH or POP operation.
The stack operates as a circular buffer if the STVREN
bit is programmed to ‘0‘ (Configuration Word 2). This
means that after the stack has been PUSHed sixteen
times, the seventeenth PUSH overwrites the value that
was stored from the first PUSH. The eighteenth PUSH
overwrites the second PUSH (and so on). The
STKOVF and STKUNF flag bits will be set on an Over-
flow/Underflow, regardless of whether the Reset is
enabled.
FIGURE 3-5:
 2010 Microchip Technology Inc.
Note 1: There are no instructions/mnemonics
Stack
called PUSH or POP. These are actions
that occur from the execution of the
CALL, CALLW, RETURN, RETLW and
RETFIE instructions or the vectoring to
an interrupt address.
TOSH:TOSL
TOSH:TOSL
3-3
ACCESSING THE STACK EXAMPLE 1
and 3-4). The stack space is
0x0D
0x0C
0x0E
0x0B
0x0A
0x0F
0x1F
0x09
0x08
0x07
0x06
0x05
0x04
0x03
0x02
0x01
0x00
Preliminary
0x0000
3.4.1
The stack is available through the TOSH, TOSL and
STKPTR registers. STKPTR is the current value of the
Stack Pointer. TOSH:TOSL register pair points to the
TOP of the stack. Both registers are read/writable. TOS
is split into TOSH and TOSL due to the 15-bit size of the
PC. To access the stack, adjust the value of STKPTR,
which will position TOSH:TOSL, then read/write to
TOSH:TOSL. STKPTR is 5 bits to allow detection of
overflow and underflow.
During normal program operation, CALL, CALLW and
Interrupts will increment STKPTR while RETLW,
RETURN, and RETFIE will decrement STKPTR. At any
time STKPTR can be inspected to see how much stack
is left. The STKPTR always points at the currently used
place on the stack. Therefore, a CALL or CALLW will
increment the STKPTR and then write the PC, and a
return will unload the PC and then decrement the STK-
PTR.
Reference
accessing the stack.
Note:
STKPTR = 0x1F
STKPTR = 0x1F
Initial Stack Configuration:
After Reset, the stack is empty. The
empty stack is initialized so the Stack
Pointer is pointing at 0x1F. If the Stack
Overflow/Underflow Reset is enabled, the
TOSH/TOSL registers will return ‘0’. If
the Stack Overflow/Underflow Reset is
disabled, the TOSH/TOSL registers will
return the contents of stack address 0x0F.
PIC16F/LF1946/47
ACCESSING THE STACK
Care should be taken when modifying the
STKPTR while interrupts are enabled.
Figure
through
Stack Reset Enabled
(STVREN = 1)
Stack Reset Disabled
(STVREN = 0)
Figure
DS41414B-page 49
for examples of