clearing speed

Hello there xD this is my first post
well im making a serial iterface to control the lcd
and i want to make my own prtocol
so when i send a 211 (ascii code)
the pic 16f877 clear the lcd

im using the xorlw instruction to compare:

when i receive an interruption from usart
MOVF RCREG
XORLW .211
BTFSS STATUS,Z
GOTO EXIT
CALL CLEARLCD
;followed by other comparations

as u can se i want to compare more numbers but i want to know if the status,z will be ready (cleared again) when i do the next comparation

the question is how many instructions or time does the Z needs to be cleared by itslf

if the answer is a lot xD, can i clear it by software? (bcf status,z)


well i hope u can understan what i say because im not pretty good in english xD, thanks


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Forget it >_<
The datasheet says that if is not zero, the STATUS,Z will be cleared automatically
So with each comparation, it will show if is or not a zero