PIC16LF1906-E/MV Microchip Technology, PIC16LF1906-E/MV Datasheet - Page 36

• Manufacturer Part Number: PIC16LF1906-E/MV
• Description: 14KB Flash, 512B RAM, LCD, 11x10b ADC, EUSART, NanoWatt XLP 28 UQFN 4x4x0.5mm TU
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 16Fr

Specifications of PIC16LF1906-E/MV

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: LIN, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 25
• Program Memory Size: 14KB (8K x 14)
• Program Memory Type: FLASH
• Eeprom Size: -
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 3.6 V
• Data Converters: A/D 11x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 28-UFQFN Exposed Pad
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PIC16LF1904/6/7
3.4
All devices have a 16-level x 15-bit wide hardware
stack (refer to Figure 3-5). The stack space is not part
of either program or data space. The PC is PUSHed
onto the stack when CALL or CALLW instructions 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:
DS41569A-page 36
Note:
Stack
There are no instructions/mnemonics
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
ACCESSING THE STACK EXAMPLE 1
0x0D
0x0C
0x0F
0x0E
0x0B
0x0A
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
STKPTR.
Reference
of 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.
Figure 3-5
ACCESSING THE STACK
Care should be taken when modifying the
STKPTR while interrupts are enabled.
through
Stack Reset Enabled
(STVREN = 1)
Stack Reset Disabled
(STVREN = 0)
 2011 Microchip Technology Inc.
Figure 3-8
for examples