Clear RD4-RD7 w/o affecting RD0-RD3

[valemike]

Suppose I initially had TRISD set up like:

port_d = 0xF0; // Preload RD0-RD3 with 0000
TRISD = 0xF0; // Set the tris register

As you can see, RD4-RD7 are inputs, while RD0-RD3 are outputs.
I now want to change RD4-RD7 into outputs (i'm doing Enhanced CCP, but that isn't relevant to my question).

How do i preserve the values in RD0-RD3?

I've thought of:

temp_d = port_d;
temp_d = temp_d | 0xF0; // next manipulate the bits in temp_d
port_d = temp_d;
set_tris_d(0x00);

or maybe i should write:

temp_d = port_d;
temp_d = temp_d | 0xF0;
lat_d = temp_d;
set_tris_d(0x00);

Which is correct? Preloading port_d? or preloading LATD?

Thanks,
Mike

[Mark]

Better to use the LAT register. Look in the datasheet for read modify write to get a better understanding of why.