18f1320 - Tris = Ok, Lat = ?

UTMonkey

Member

• Dec 7, 2007

• #1

Hi All,

I have been reviewing all the documentation I have on PICs, now I have my first PIC to program I am trying to make sense of my first Blinky LED program (I think BlueRoomElectronics wrote it).

It all makes sense except I am not sure what LATA does (Latch A)?

Any help gratefully received.

Mark

 

futz

Active Member

• Dec 7, 2007

• #2

UTMonkey said:

except I am not sure what LATA does (Latch A)?

Click to expand...

Use LATA/LATB instead of PORTA/PORTB. It cures the Read/Modify/Write problem. You can read about it in the "PICmicro® 18C MCU Family
Reference Manual" It's a MUST-READ!

 

Last edited: Dec 7, 2007

blueroomelectronics

Well-Known Member

• Dec 7, 2007

• #3

You can use PORTx in place of the LATx command but as futz mentioned the LATx gets around the RMW problem.

 

UTMonkey

Member

• Dec 7, 2007

• #4

Thanks Guys, I am enjoying this.

 

blueroomelectronics

Well-Known Member

• Dec 7, 2007

• #5

Glad to hear it, try the PORT instruction should still work.
The 18F1320 can be reprogrammed at least 100,000 times so you'll probably never wear it out

 

UTMonkey

Member

• Dec 7, 2007

• #6

I'm giving it a good go, believe me.

 

Oznog

Active Member

• Dec 7, 2007

• #7

Well you need to use the PORT register while reading (TRIS must be 1 for any pin you're reading). Always use the LAT register while assigning the output pin (TRIS must be 0 for those pins). PORT does technically work but has the read-modify-write prob and even though that doesn't show up in most circumstances there's no reason at all to be using it.