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For the initialisation of an I/O in the pic the datasheet indicates to clear set the TRIS correctly and clear both PORT and LAT bits. I thought I understood why and the program works. When looking at the disassembly however the PORT clearing and LAT clearing generate the same instructions. I did not look further but I think that the PORT bits are cleared as a result of the LAT bits clearing.

Is there a specific reason that the datasheet (asm) indicated to clear both PORT and LAT and in C it boils down to one action only on LAT.

C code example lead both to identical asm after compilation:

PORTAbits.RA0 = 0;
LATAbits.LATA0 = 0;
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  • \$\begingroup\$ What is the C code and what is the assembly generated? \$\endgroup\$
    – Eugene Sh.
    Commented May 17, 2017 at 18:39
  • \$\begingroup\$ Samples of C included \$\endgroup\$
    – Decapod
    Commented May 17, 2017 at 18:45
  • \$\begingroup\$ Still, it is incomplete without the assembly generated.. BTW, can you look around your headers ans see the exact definition of PORTA and LATA ? Could it be that they are just the same register? \$\endgroup\$
    – Eugene Sh.
    Commented May 17, 2017 at 18:49
  • \$\begingroup\$ Reason found. In the lib used there was a macro with a typo leading to this behaviour. After correcting this both registers are handled the same way as in the specsheet \$\endgroup\$
    – Decapod
    Commented May 17, 2017 at 19:07
  • \$\begingroup\$ Is it the vendor provided macro or some homebrew/thirparty? \$\endgroup\$
    – Eugene Sh.
    Commented May 17, 2017 at 19:07

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