Hey Yogi,
blimey only just noticed your comments: just a quick note, the confusion is caused as the pinouts on my diagram mean you can use a a 27c040 (512k) chip /o\ sorry about any confusion there - the pinout for 27c010 (128k) / 27c020 (256k) have a slightly different assignment for pin 31... On a 27c040 pin 31 is A18 y'see... v. odd that pin 1 would be complaining although tbh best practice is def to tie any floating pins - didn't think that would cause any issue tho - at least it does not on the FamicomWell done for fiddling and getting it working on the NES
I'll try and change the guide to reflect that soon! ^
Hi there ne7! Thanks again for your guides, they are very helpful to me. Prior to your posts, I've only messed with Atari stuff and MCU projects. So all things Nintendo are quite new to me and your guides have been a great help introducing me to 'MMC land'
As to pin1, I've seen some datasheets that do advise Vpp tied to Vcc but that doesn't necessarily mean that all manufactures would require it. So I would guess some eprom may not have a prob with it floating.
With pin 31 it's a little different, being /PGM on the '010 and '020 devices. With the unused half of the 512k of a '040 on a MMC1 cart, A18 is moot as long as the EPROM is filled with the ROM image be it 128K or 256K.
Another point that may have some impact is the handling of /OE and /CE. Not sure how much but there is a timing difference between the two, with /OE being the faster to respond given /CE tied low. Probability wouldn't make much difference on a fast Flash or EPROM (<90nS device) but could be an issue with an older 250nS rom.
Anyway my adventures were all with the latest version of NTRQ and it seem to be the easier of Neil's SxROM titles. I haven't tried the SXROM conversion; mainly because of the reported problems with NES carts and MMC1 versions. Since then I have found a great Flash cart project by INL over at NesDev that runs PR8 and Pulsar. You may want to check out his shop, he plans to start building FC carts soon. He has sourced a 3rd party cart case, so now he can design a standard board outline based on it.
Thanks again,
Yogi
Last edited by yogi (Feb 14, 2014 6:17 pm)