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Steve



Joined: 10 Sep 2005
Posts: 10
Steve
Hi.

I need some help testing a bit in an 8-bit register. For example, how would I go about reading bit 4 of that specific register? I've looked at 'test' but I'm not really sure how to go to a specific position in the register and test the bit. How would I do this?

Thank you,

- Steve Smile
Post 23 Apr 2006, 18:53
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
f0dder
test reg, 2^bit Razz

so, to test bit 4, you'd calculate 2^4 (two raised to the power of four). That's 16. Then, "test reg, 16". Now you can do something like "sete al" to set AL to the bitvalue.

There's also the "BT" (bit test) instruction - check out an x86 reference for more information.
Post 23 Apr 2006, 20:44
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Steve



Joined: 10 Sep 2005
Posts: 10
Steve
Thanks, f0dder. Very helpful as always. Smile
Post 23 Apr 2006, 21:09
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