Hi everybody!

I've got some quick questions about port 0, and was hoping someone could provide me with some yes/no answers. Hopefully I've got everything right, and if not I'll head back to the 8051 bible and figure out where I went wrong.

I'm using the SST89C54.

1) I'm using port 0 as a keypad input, but instead of running it directly from the keypad to the controller I'm interfacing through some 74LS148s (keypad is 12 pin, not 8 pin matrix). Am I correct in the assumption that I don't need any pullup resistors, as I would if I connected a 8 pin matrix directly to port 0 (as I did on my last project), when the input actually comes from the 148s?

2) If I'm only using port 0 for input, always, do I need to set P0 to 0xFF every time I want to read from the port (or is once enough)?

On a funny side note, I had some serious issues with my breadboard prototype that I couldn't figure out. Everytime I put the microcontroller in, all the ports would pulse and none of my programs would work. Even a simple slow toggle of port 3 was whacked. Funny thing was, when sitting in my bootstrap loader, port 3 toggled just fine. Moral of the story, always tie EA to high.

Anyway, I don't expect anyone remembers me but I posted a message here last summer asking for a DTMF chip. I did find one from Mouser (thanks Erik M.) that works great. My project is coming along nicely, and I expect to start milling PCBs next week (unless I hit some more unexpected problems).

There's a little bit of information about my project on my website, which is available in my profile, if anyone wants to have a peek.

Thanks!