TI and Freescale designate PA1 as Port A bit 1.
But Microchip uses RA1 to refer to the same meaning. So what exactly does R stand for ?
\$\begingroup\$
\$\endgroup\$
1
-
\$\begingroup\$ I would say "register" or "registered", but I can find no proof of such. \$\endgroup\$– Ignacio Vazquez-AbramsCommented Feb 14, 2015 at 3:30
Add a comment
|
1 Answer
\$\begingroup\$
\$\endgroup\$
2
Microchip lists any memory-mapped I/O as Special Function Registers. So RA1 is bit 1 of the Port A Register.
In addition to the ports, which are accessed through registers PORTA, PORTB, PORTC etc., there are also tri-state registers (TRISA, TRISB, TRISC etc.) which set up whether a pin is an input (1) or output (0).
At least for the smaller PICs, Microchip also refers to its static RAM (which may be as little as 16 bytes) as General Purpose Registers (GPR).
The SFRs and GPRs are mapped into the same address space (i.e. the I/O ports can be addressed like RAM).
-
\$\begingroup\$ I figured as such, but referring RA0, RA1,... on the schematics as registers is so lame ! \$\endgroup\$ Commented Feb 14, 2015 at 7:29
-
1\$\begingroup\$ @user1502776 For what its worth, RA0, RA1 etc are the names of the individual bits in the PORTA register, so they are just saying pin RA1 is controlled by bit RA1 which makes sense. \$\endgroup\$– tcrosleyCommented Feb 14, 2015 at 8:50