PIC16F15213 datasheet(49/420 Pages) MICROCHIP

49 / 420 page

9.4

PCL and PCLATH

The Program Counter (PC) is 15 bits wide. The low byte comes from the PCL register, which is a readable and

writable register. The high byte (PC[14:8]) is not directly readable or writable and comes from PCLATH. On any Reset

the PC is cleared. Figure 9-8 shows the five situations for the loading of the PC.

Figure 9-8. Loading of PC in Different Situations

Filename:

10-000042A.vsd

Title:

LOADING OF PC IN DIFFERENT SITUATIONS

Last Edit:

7/30/2013

First Used:

PIC16F1508/9

Note:

PCL

PCH

PCLATH

Instruction

with PCL as

Destination

GOTO,

CALL

CALLW

BRW

BRA

ALU result

OPCODE

[10:0]

PC + W

PC + OPCODE

[8:0]

Rev. 10-000042A

7/30/2013

9.4.1

Modifying PCL

Executing any instruction with the PCL register as the destination simultaneously causes the Program Counter

PC[14:8] bits (PCH) to be replaced by the contents of the PCLATH register. This allows the entire contents of the

Program Counter to be changed by writing the desired upper seven bits to the PCLATH register. When the lower

eight bits are written to the PCL register, all 15 bits of the Program Counter will change to the values contained in the

PCLATH register and those being written to the PCL register.

9.4.2

Computed GOTO

A computed GOTO is accomplished by adding an offset to the Program Counter (ADDWF PCL). When 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 Application Note AN556, “Implementing a Table Read” (DS00556).

9.4.3

Computed Function Calls

A computed function CALL allows programs to maintain tables of functions and provide another way to execute state

machines or look-up tables. When performing a table read using a computed function CALL, care should be

exercised if the table location crosses a PCL memory boundary (each 256-byte block).

If using the CALL instruction, the PCH[2:0] and PCL registers are loaded with the operand of the CALL instruction.

PCH[6:3] is loaded with PCLATH[6:3].

PIC16F15213/14/23/24/43/44

Memory Organization

Preliminary Datasheet

DS40002195A-page 49

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