PIC16F636-I/P Microchip Technology Inc., PIC16F636-I/P Datasheet - Page 28

• Manufacturer Part Number: PIC16F636-I/P
• Description: 14 PIN, 3.5 KB FLASH, 128 RAM, 12 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F636-I/P

• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 12
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 14-pin PDIP
• Programmable Memory: 3.5K Bytes
• Ram Size: 128 Bytes
• Speed: 20 MHz
• Timers: 1-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC12F635/PIC16F636/639
2.3
The Program Counter (PC) is 13 bits wide. The low byte
comes from the PCL register, which is a readable and
writable register. The high byte (PC<12:8>) is not
directly readable or writable and comes from PCLATH.
On any Reset, the PC is cleared. Figure 2-5 shows the
two situations for the loading of the PC. The upper
example in Figure 2-5 shows how the PC is loaded on a
write to PCL (PCLATH<4:0>
example in Figure 2-5 shows how the PC is loaded
during a CALL or GOTO instruction (PCLATH<4:3>
PCH).
FIGURE 2-5:
DS41232B-page 26
PC
PC
12
12 11 10
2
PCL and PCLATH
5
PCH
PCLATH<4:3>
PCH
PCLATH
PCLATH<4:0>
8
PCLATH
8
7
7
LOADING OF PC IN
DIFFERENT SITUATIONS
PCL
PCL
11
8
PCH). The lower
0
0
Instruction with
Opcode<10:0>
ALU Result
GOTO, CALL
Destination
PCL as
Preliminary
2.3.1
A computed GOTO is accomplished by adding an offset
to the program counter (ADDWF
performing a table read using a computed GOTO
method, care should be exercised if the table location
crosses a PCL memory boundary (each 256-byte
block). Refer to the Application Note AN556,
“Implementing a Table Read” (DS00556).
2.3.2
The PIC12F635/PIC16F636/639 family has an 8-
level x 13-bit wide hardware stack (see Figure 2-1).
The stack space is not part of either program or data
space and the Stack Pointer is not readable or writable.
The PC is PUSHed onto the stack when a CALL
instruction is 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. This means that
after the stack has been PUSHed eight times, the ninth
push overwrites the value that was stored from the first
push. The tenth push overwrites the second push (and
so on).
Note 1: There are no Status bits to indicate stack
2: There are no instructions/mnemonics
COMPUTED GOTO
STACK
overflow or stack underflow conditions.
called PUSH or POP. These are actions
that occur from the execution of the CALL,
RETURN, RETLW and RETFIE instructions
or the vectoring to an interrupt address.
© 2005 Microchip Technology Inc.
PCL). When