Combining Ports?

Question

I am using the P18F8720's many io pins to write usart data to a 32K NVRAM. I don't have room for an address data latch so I am assigning:

Address(0..7) to PortD Address(8..15)to PortJ Data(0..8) to PortE WE/ to PortB.0 OE/ to PortB.1

At least that is what I thought I wanted to do before I started to write the code. Is there some way to combine PortD and PortJ to make a

16 bit register? Or some way to move values from the upper byte of Address to PortJ and the lower byte to PortD?

I could use a chain of conditionals to move Address bytes to Ports but it seems clunkier than necessary.

Thanks much, Ed V.

Anthony Marchini · Accepted Answer

This chip appears to do all data operations as byte anyways, so it should be a simple matter to transfer the high and low bytes to the respective ports. The question makes me think that you are perhaps using C, in which case there should be a way to get a pointer to the "two byte int" or something like that, then you just get one and then the next byte out of it like this :

int reg16; byte * x; x = & reg16; PortJ = *x++; PortD = *x;

I am just guessing about the C part, since the question appears to be moot by virtue of the chip operation. T.

EdV · Answer

Thanks.I found a C language refrence and ended up using right shift and itworked just fine.I will look into your pointer suggestion as I need to use that part ofmy brain more often.Ed V.Anthmake acaseof

Anthony Marchini · Answer

The nice thing about pointing to the register is that it doesn't destroy the original as shifting will do. You won't have to make a copy before shifting it 8 bits and loading it out.T.

Combining Ports?

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