Sega Genesis rom/sram address mapping

Discussion of development of software for any "obsolete" computer or video game system. See the WSdev wiki and ObscureDev wiki for more information on certain platforms.
lidnariq
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Joined: Sun Apr 13, 2008 11:12 am

Re: Sega Genesis rom/sram address mapping

Post by lidnariq »

On the SNES, the /RESET pin is driven via a 1k resistor, so your transistor's base current can be pretty large without a problem.

(https://wiki.superfamicom.org/schematic ... ematic-490 - signal "/RESOUT1" from PPU2 via R74 1k to everything else)

On the Genesis, the two reset pins (/MRES and /VRES, cartridge pins B2 and B27) have 47kΩ pullups instead, so you have a very small amount of current available for the transistor.

(https://gamesx.com/wiki/doku.php?id=sch ... _megadrive - "CPU and custom chips" - look top center above IC5, to find R1 47k pullup to C64 10µF, and bottom left between IC1 and IC4, to find R46 47k pullup)
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