Is it possible to read a WKEN_B register?

Bill Franke

To read the contents of the WKPND_B register, a “mov !rb, w” instruction is used to copy the contents of the pending reg. into W (reverse transfer). (I found that this is also how to “read” the read registers of the SX48/52 timers by the way.) Does anyone know if this works on the WKEN_B registers, also? How about a TRIS register?

Specifically, I want to be able to change only one bit of the WKEN_B register without affecting the other bits. If I can read it, I can AND mask it to change the specific bit that I want.

It’s too bad Parallax didn’t make it possible to do a “ setb !rb.6 ” instruction.

James Newton

You have to keep a "shadow" register which records the state of any changes made to the WKPND_B register. In each place where you change WKPND_B, first change the shadow register. Then when you want to change a bit, you do it in the shadow, and copy that to WKPND_B.

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Bean

Bill,
· On the SX48 the TRIS registers are readable and writeable. You can read the register, change one bit, and write it back.

· But the WKPND_B is one of the rare registers that are write-only on the SX48.

Bean.

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Bill Franke

Thanks guys

Bill F