I have a little Parallax GPS module which uses 3 pins, 5vDC, gnd and a bidirectional serial IO pin.

What would be the easiest way to connect the SIO pin to a serial port given that it is bidirectional?

I prefer to use a proper serial port as the SIO pin expects 4800/8/1/n, but I'm not sure how to ...

Im going to run around town today - see if i can find someone with an EEPROM programmer. Small town of 4000 people Im expecting to find maybe 2 if Im lucky

Any chance of a quick sketch of that single step button schematic Garth?

Unfortunately I have no test equipment.

At the moment, my testing has relied on an LED connected to GND. I use this to check the voltages on pins of the 28C256 (32kx8 EEPROM).

The one time it worked successfully, all the address pins were low expect for A0 and A1 which I expected as the code was ...

Now that I've dug through all the circuitry, I've 'almost' found the problem :)

Biggest problem wasnt the main board at all, but the EEPROM programmer - I had tied WE high so it could never write. Once I fixed that, the EEPROM programmed and ran in the main board properly... once :(

I think when i ...

Guess I've caught your disease Garth.. Meant to say $4C, but wrote $43.

I'm just tracing my main circuitry as I noticed there are 'some' wires not connected. Its been a good few months since I tested it with the NOP generator, so I can't remember what state it was in when I got annoyed that I ...

Oops - put everyone wrong. I am writing $00 to $FFFC, and $80 to $FFFD. My bad.

Slightly confusing Garth :)

High-byte first then, $00, $80

To me, $00,$80 would be low-byte first. Could you clarify? I think both you and 8BIT are saying it should be $FFFC=$80, and $FFFD=$00??

Not sure where I got $63, but I printed out the opcode sheet this morning and realised it was $43, but ...

If I was to do the following, should it enter a loop?

write 0x80, 0x00 to 0xFFFC, 0xFFFD

write 0x63, 0x00, 0x80 to 0x8000, 0x8001, 0x8002. These are the opcodes for JMP $8000 (I hope).

From my understanding of assembly code, the processor should start execution at $8000, and then keep jumping ...

What I planned to do was have a single ISR routine in the standard place which, rather than handling the IRQ's directly, would read the 8-3 encoder and the jump to the appropriate ISR's routine.

There would only be 1 IRQ line per expansion card, and it would be up to the individual routine to ...

Has any tried any kind of IRQ expansion system??

What I want to do is provide a 'seperate' IRQ for each expansion slot - up to 8 maximum. Then some how (this being the bit Im stuck on :) ) catch the IRQ's in a 8-3 encoder and also trigger the uP IRQ\ line. The uP would then read the 8-3 encoder and ...

Has anyone proposed any kinda of structured uniform open-ended design for a 6502 based system?

Something along the lines of minimum required functionality to be conforment, memory map specifications etc etc. It would still allow individuals to build their systems any way they wanted, but when ...

Now that I re-read that, might be a conusion - I meant 1 or 2 Mhz, but I guess that doesnt change the fact I can be 'rough-as-guts' on the circuitry so to speak.

The reason I'm going with the expansion ports isnt to give me more space. I just like the idea of expansion cards - in other words, I can ...

Since I'm running my system at 1/2 Mhz, I thought I could just interface directly to the address/data busses (perhaps with buffering?)

The reason I asked about the drive current is that I am going to have 8 plug in slots to make playing around easier. All the slots will have A0-A4 connected to them ...

I must be searching for the wrong terms because Im sure I've seen it mentioned but I can't seem to find the info for the drive current of A0-A15 and D0-D7 of a 6502.

I tried to work it out from the datasheet, but.. well.. I'm too stupid :)

Could someone post the link to the topic, or just repeat ...

I have an 18VA transformers here with taps for 12,15 and 18 volts.

Apart from the fact that the 12v tap isnt working for whatever reason, the thing weighs a ton and is about 1.5" x 2".

How do power packs (like my lil 7v one) convert from 240v -> 7v without a huge transformer??

I might expect a ...