Can I use J5 of PIC based core as a "LOGIC" input?

Testing/Troubleshooting
1

Hello,

 

i want to connect LRQ output pin of SP0256 chip (0V - 2,5V) to the PIC core via 1 Pin on J5 configured as an input.

That input signalise, that the buffer of SP0256 is full.

 

please take a look at the pin configuration of LRQ inside sp0256 manual:

http://www.futurebots.com/spo256.pdf

 

From the SP0256-AL2 manual:

 

LOAD REQUEST. LRQ is a logic 1

output whenever the input buffer

is full.

 

So I had found the hardware configuration of using J5 as digital input for buttons or rotary encoder:

http://www.ucapps.de/mios/j5_din.pdf

 

Do I have to add also a 10k (or other value) for that pin like in that configuration above, to avoid a short cut on PIC core, or can i direct connect the wire?

 

Thank you.

 

Greetings, rio.

2

Looking at the SP0256 spec you sent, this is a 5v device just like the PIC core.  The LRQ output can drive 2 LS-TTL loads with a ZERO voltage of 0.5v and a ONE voltage at 2.5 volts.  The PIC running on a 5 volt power supply can input a ZERO for anything less than 0.8v and a ONE for anything over 2.0 volts.  So you can directly connect any of the SP0256 outputs to the PIC inputs without any issues.  No resistor necessary.

 

When you are debugging your code I would remove the SP0256 from the socket and make sure that your software has configured the TRIS registers correctly.   You don’t want to drive one of the SP0256 outputs with outputs from the PIC.  You might blow up your SP0256 output pin if your PIC is configured wrong.