Guys, how would I go about extending an UNROM cart for larger chips? I guess that would be like converting the cart into UOROM, right?
The LS161 latches 4 bits, correct? But UNROM only uses 3 of those. Would this conversion be as simple as connecting the unused bit from the LS161 to A17 on the chip?
Also, is there any way I could add mirroring control without too much complication? I'm gessing not, so I might just add a manual switch.
Thanks for the help!
EDIT:
After thinking a while about how an UNROM cart works, I'm assuming it can't be as simple as connecting the unused output from the 161 to the chip.
I figured that the output of the 74161 probably goes to the 7432 to be OR'ed with A14 comming from the NES, so that the higher bank can be hardwired.
Now, I'm not very good with hardware, but by looking at how those chips work this must be the way the mapper works. If it really is like this, then I'd have to wire the output from the 74161 into the 7432, and the output of that into the PRG chip. Does that sound right?
The LS161 latches 4 bits, correct? But UNROM only uses 3 of those. Would this conversion be as simple as connecting the unused bit from the LS161 to A17 on the chip?
Also, is there any way I could add mirroring control without too much complication? I'm gessing not, so I might just add a manual switch.
Thanks for the help!
EDIT:
After thinking a while about how an UNROM cart works, I'm assuming it can't be as simple as connecting the unused output from the 161 to the chip.
I figured that the output of the 74161 probably goes to the 7432 to be OR'ed with A14 comming from the NES, so that the higher bank can be hardwired.
Now, I'm not very good with hardware, but by looking at how those chips work this must be the way the mapper works. If it really is like this, then I'd have to wire the output from the 74161 into the 7432, and the output of that into the PRG chip. Does that sound right?