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Recover IC PIC16F687 Software

The Program Counter (PC) is 13 bits wide. The low byte comes from the PCL register, which is a recoverable and writable register which can be used for Recover IC PIC16F687 Software. The high byte (PC<12:8>) is not directly recoverable or writable and comes from PCLATH. On any Reset, the PC is cleared. Figure 2-9 shows the two situations for the loading of the PC. The upper example in Figure 2-9 shows how the PC is loaded on a write to PCL (PCLATH<4:0> → PCH). The lower example in Figure 2-9 shows how the PC is loaded during aCALL or GOTO instruction (PCLATH<4:3> → PCH).

The PIC16F687 devices have an 8-level x 13-bit wide hardware stack. The stack space is not part of either program or data space and the Stack Pointer is not recoverable 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).

Executing any instruction with the PCL register as the destination simultaneously causes the Program Counter PC<12:8> 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 5 bits to the PCLATH register.

When the lower 8 bits are written to the PCL register, all 13 bits of the program counter will change to the values contained in the PCLATH register and those being written to the PCL register after Recover IC PIC16F687 Software.

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