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To make a 16-bit ROM from two 8-bit you only need to connect their address lines together, and use data lines of first chip as D0-D7 and data lines of second chip as D8-D15.
If you need to make a large ROM from few smaller ROMs, you may need to use a decoder that will enable chips depending from the most significant address lines.
If you need to make a large ROM from few smaller ROMs, you may need to use a decoder that will enable chips depending from the most significant address lines.
I believe that 2 8-bit chips can be used to simulate a 16-bit chip without any extra hardware... just connect all address line to both chips and combine their 8-bit outputs for a total of 16 bits. If you need more than 2 chips you're gonna need a decoder in order to have the highest address line(s) select which pair of chips are to be used.
So we're up to a 74HC139 and two to four pairs of flash chips.
tokumaru wrote:
I believe that 2 8-bit chips can be used to simulate a 16-bit chip without any extra hardware... just connect all address line to both chips and combine their 8-bit outputs for a total of 16 bits. If you need more than 2 chips you're gonna need a decoder in order to have the highest address line(s) select which pair of chips are to be used.
OK so if I was to spread 8mb across 4 2mb chips I assume I can use a 74ls08 as the decoder but what and where would I wire it like please?
tepples wrote:
So we're up to a 74HC139 and two to four pairs of flash chips.
so a 139 not a 08?
Don't do it. Use a 27C160. It solders directly into most PCBs. Sega did not alter pinouts like Nintendo. Also the game mentioned is 2 megabytes, not 1. You'd need 8 of those 2 megabit chips for a 16 megabit game.
You can simulate a 16bit eprom with two 8bit chips but again this is silly. Just buy a 16bit programming adapter if you have to do so or just get someone to program a 27C160 for you.
Or just buy a EverDrive MD, one of the best Flash carts out there, and the best for Sega Genesis easily.
http://krikzz.com/everdrive-md.html
http://shop.retrogate.com/Everdrive-MD-EDMD.htm
You can simulate a 16bit eprom with two 8bit chips but again this is silly. Just buy a 16bit programming adapter if you have to do so or just get someone to program a 27C160 for you.
Or just buy a EverDrive MD, one of the best Flash carts out there, and the best for Sega Genesis easily.
http://krikzz.com/everdrive-md.html
http://shop.retrogate.com/Everdrive-MD-EDMD.htm
MottZilla wrote:
You can simulate a 16bit eprom with two 8bit chips but again this is silly. Just buy a 16bit programming adapter if you have to do so or just get someone to program a 27C160 for you.
16bit chips it is then.
If you are interested in alot of Genesis games I really recommend the EverDrive flash cart still. I really like mine. It's not very expensive and it's high quality and is just awesome. Beats fooling with EPROMs.