ah, i see. i'll have to do that then. thanks for the info. and i'm not using LEDs to test anymore, i've actually using monitor firmware i've been writing and i connect to a laptop's parallel port as an I/O terminal. i guess i've been lucky so far, i haven't seen any problems but i will use an LS74 ...

Without looking at the schematics, I would not recommend using a '373 as output latch. This almost guarantees glitches on the output signals.

When the '373 is enabled, the signals are "transparent" according to my data book. So if they are enabled when phi2 goes high, but the CPU has not (yet) put ...

A lot of the later SRAM cache chips were 3.3v parts, like the Aliance AS7C3256. While most will tolerate 5v as an absolute maximum, they might not run at that very well or for very long. They do, however, seem to work fine in a 5v circuit if powered through a diode. This gives them about 4v and ...

ah, of course! that makes sense. and i guess the "damage" wasn't permanent. i am now using one i thought went bad but it's working just fine. i assumed they went bad because even after turning it off and on or resetting a few times, the errors kept happening until i tried a different chip.

i added ...

any ideas off the top of your collective heads, let me know please -- but in the mean time i'm going to create an actual schematic of the circuit so everything is more clear.

EDIT: sorry, i meant to post this in the emulation section not programming!

i originally wrote this for my NES emulator, but i've also used it in a few other things. it works very well, so i figured i might as well post it, in case anybody else wants to make use of it.

questions, comments, or find ...

i have been using the 32 KB SRAM cache chips for my 6502 circuit's memory. i get them from old 386 and 486 motherboards i have stashed away. there are a few different manufacturers' chips that i've been using but all have identical pinouts to the Alliance AS7C256-PC model.

these chips do work on ...

kicad looks excellent! i think i will make up some schematics for this now before it gets too much more complicated, so i can share the design when it's done. i've got it running code i wrote and stuck on a ROM that so far just splits a big string into high/low nibbles, and sends them out through a ...

Try: NOT(A15) AND Ф2 AND NOT(R/W)
I am not sure if it will work, if i got it right it should.
When using devices that don't support this kind of synchronous bus, you must always sync the enable pin with clock phase 2 of the cpu.
I've added some latches to my sbc(they do work), and if it won't work ...

what's a good program for designing a schematic? i've never done it on a computer, and i'm not that great with them in general. i don't have a lot of design experience.

that was fast! i don't actually have a circuit schematic made up, i've just been sitting over the breadboard with data sheets and experimenting. give me a little bit and i'll post a schematic. thanks.

hi, i'm new to designing/building computers but i'm creating a 6502-based computer on a breadboard. i've got it successfully running code, verified by single-stepping with the LEDs on the EEPROM data output and the values match up.

my problem is, i've now added a 74LS373N octal latch which i am ...