9.3 STATUS Register

The STATUS register contains:
  • the arithmetic status of the ALU
  • the Reset status
The STATUS register can be the destination for any instruction, like any other register. If the STATUS register is the destination for an instruction that affects the Z, DC or C bits, then writes to these three bits are disabled. These bits are set or cleared according to the device logic. Furthermore, the TO and PD bits are not writable. Therefore, the result of an instruction with the STATUS register as destination may be different than intended.

For example, CLRF STATUS will clear bits [4:3] and [1:0], and set the Z bit. This leaves the STATUS register as ‘000u u1uu’ (where u = unchanged).

It is recommended, therefore, that only BCF, BSF, SWAPF and MOVWF instructions are used to alter the STATUS register, because these instructions do not affect any Status bits. For other instructions not affecting any Status bits, refer to the “Instruction Set Summary” chapter.
Important: The C and DC bits operate as Borrow and Digit Borrow out bits, respectively, in subtraction.