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TODO.md

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  • export SN76489 symbol from leako, and import it into here and the global lib storage
  • add the address, I/O decoders
  • check the write pin on the RAM
  • add the TMS9918
  • ...and the DRAM-SRAM intercept flipflops
  • make a symbol for the cart slot
  • make a footprint for the cart slot part
  • will the power transistor setup from leako work?
  • populate all the z80 pins with labels
  • double check NMI transistor pinout, use a PNP i already stock (3906?)
  • copy digikey pn from leako for 6mm push button
  • what size of resistor should i use? looks like i started out with 0805 again for capacitors, i guess we're doing 0805 again here
  • confirm the weirdness with /WR or WR for /WE on 76489
  • finish switching to the cypress THT 62256 since i already have some?
  • copy video and audio output circuits from leako
  • double check the decoder weave for the controllers
  • find 74ls257
  • usb power input (with power flags)
  • power switch
  • add a spare footprint for an emergency inverter
  • cart slot is actually 0.125"
  • print and check cartridge interference once parts arranged
  • stuff all this into a board and route it
  • keyboard port? what's it even look like
  • maybe do the flange and mounting holes on the cart slot after all
  • make a decision on 150x150 - it's only 78 cents more per board and i don't think anyone cares
  • make room for mounting holes
  • either find a new cartridge slot or make sure parts aren't hitting the mounting holes - YES - EDAC 396-044-520-201
  • [SF-7000] look into the sf-7000 i/o range that fabiodl mentioned - "The sg-1000 does not allow connecting the SF-7000 because the joystick/SK1100 takes the IO range 0XC0-0XFF, while the SF-7000 requires the range 0xE0~0xFF."
  • [SF-7000] defeat keyboard/joystick decode if a5 is high
  • [SF-7000] synthesize /IOWR and /IORD and pass to cartridge
  • wire at least 2k (SG-1000 II) of the 32k 62256
  • [Onboard ROM] wire up onboard DIP ROM
  • [Onboard ROM] detect non-presence of cartridge
  • [Onboard ROM] decode EXM2 to onboard ROM if cartridge is not present
  • [Memory Mapper] 74ls74 set
  • [Memory Mapper] decode a read to upper 8k of RAM specially (trigger on a13 & /CS_WRAM maybe using a quad nand)
  • [Memory Mapper] replace 74ls74 with a different latch that emits only during upper-8k read (7474 is not tristate) - picked 74ls373, see if something better comes along
  • [Memory Mapper] Dump all the knowledge we have about the memory map into decody to make sure we actually have a 16k window, and not 32k. If we have 32k, just get rid of the mapper.
  • [Memory Mapper] does it make sense to use a '573 instead of a '373? Might be easier to route and find
  • [Memory Mapper] find a spot on the board for it
  • [Keyboard] Find out if it is possible to get 6u spacebars or if 6.25u is needed
  • [Software] RAM tester, in Z80 assembly so we can control the RAM.
  • Build a clone of the BASIC III-B cartridge to ensure /CS_WRAM pullup works
  • 24kHz LPF on audio output
  • better cap (0.22uF film?) on audio output