> > union
> > {   unsigned char   Byte;
> >     Port_t          Bits; }     PortA, PortB, PortC;
> >
> > and use it like this
> >
> > if (!PortB.Bits.bit5)
> >     PortA.Byte = 0xAA;
>
> I use something similar on occasion, but usually not for the ports.
> What is the advantage of this union/bitfield over the Hi-Tech standard
> header declarations, like
>
>   if( !RB5) PORTA = 0xaa;

My declaration isn't _the_ port, it's a variable called Port.
I grab the state of a port at a single instant in time so the code
immediately above the 'if' statement is
   PortB.Byte = PORTB;
There are a pile of bit tests that get done at each sampling time and if a
bit gets tested as a 0 and then gets tested again as a 1, the logic flow
goes all up the creek.

The PORTA = 0x55 was just as an example.

This code gets used on several products that use different chips and pin
assignments. This is a fairly efficient and tidy way of moving bits around
so that they can be manipulated individually and/or collectively as bytes
and mask values.

Steve.

==========================================
Steve Baldwin                          Electronic Product Design
TLA Microsystems Ltd             Microcontroller Specialists
PO Box 15-680, New Lynn                http://www.tla.co.nz
Auckland, New Zealand                     ph  +64 9 820-2221
email: steve@tla.co.nz                      fax +64 9 820-1929
=========================================

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