PICC pointer to PORTs possible?

Hi I've just beginned programming pics in C and I was trying to "merge" ports C and D together in one 16bit variable, does anyone have an idea on how can i do this?


Thank you

serj.t.s said:

Hi I've just beginned programming pics in C and I was trying to "merge" ports C and D together in one 16bit variable, does anyone have an idea on how can i do this?

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Why would you want to?.

You could certainly easily write a function that takes a 16 bit variable and place the top eight bits to one port, and the bottom to another. However, I don't do C, but it's easy in any thing else, so presumably will be in C?.

Hi Nigel, I just though it would be more efficient and simple because I'll be manipulating those registers together with shifts and other operations but I guess I'll have to do it yout way.

Thanks for the reply.

It would only take 4 words, and 4 instruction cycles (4uS with a 4MHz clock) in assembler - it doesn't get any simpler and more efficient than that!

The direct answer is, you can if you compiler allows it.

When asking C questions please let us know what processor and compiler you are using. They differ enough that one needs to know.

I use CCS which has #bit and #byte directives that allow that sort of thing. But no #word. It may exist on 16 bit compilers.

A better, compiler independant, answer is along the line of what Nigel suggested. Declare a 16 bit shadow register (just a 16 bit variable) and do you crunching with it. When needed call a function to write the top 8 bits to C and the lower to D.

If you need speed make the copy function inline.

Hi, sorry about the lack of info.

I am using the PICC compiler from HI-Tec h.

And I ended up doing:
PORTC = temp;
PORTD = (temp >> 8) & 0xFF;

This compiler doesn't have BYTE(temp) or char(temp), but it worked this way. Btw I don't think the 0xFF mask is necessary. I guess I'll try it out tomorrow, i am soo lazy

You do not need the mask if temp is a 16 bit unsigned. Good chance the your integers are unsigned by default.