FlashROM 8300

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Summary

Adapter board to use a flash chip for the system rom in a NEC PC-8300.

PCB: https://oshpark.com/shared_projects/6SBEGtlg

BOM: https://www.digikey.com/short/z8293n

Source: https://github.com/bkw777/aDIPters

References

Mask rom datasheet

File:UPD23C1000A.pdf

Old reference about pin-compatible parts:

https://www.web8201.net/Files/LIBRARY_web8201/NECPC8300_System_ROM_EPROM_Replacement.html

Compatible flash/eeprom/eprom chips that can be used on this board (LCC or TSOP)

Without R3 installed:

39SF010 https://www.digikey.com/short/z88hb8
29SF010
29EE010 https://mou.sr/39tR5zu
29F010
28C010

With R3 installed (47K):

28F010
27SF010
27C010

Any speed and any temperature range is ok.

Any TSOP32 or LCC32(7x9) package is ok.

ROM images

NEC PC-8300 system rom: File:831000-438.bin
NEC PC-8300 system rom, Y2K patched: File:831000-438-y2k.bin

Directions

Building

See FlexROM_100 to see how to do the dip legs.
Search youtube for "drag solder" to see how to solder the TSOP legs with an ordinary soldering iron.

Suggest installing parts in this order:

  1. Legs - The holes for the the legs are intentionally small and a fairly close fit on the legs. The legs should be installed first to avoid the problem where if you accidentally get solder in some of the holes while soldering the other parts near by, it can be difficult to wick the holes clean enough to insert the legs after that without vacuum.
  2. R1, R2 - Especially R1 is surrounded by other parts, and especially if you are using a PLCC chip, the corner of the PLCC actually extends over top of part of of R1. So it's easiest to install R1 before anything else, definitely before the PLCC chip if using that type instead of TSOP.
  3. TSOP or PLCC chip - Especially if you're using the 8x20mm TSOP chip, the jumper pins would be in the way and make it difficult to solder the TSOP legs.
  4. Jumper pins - Flush-cut the posts on the bottom of the board after soldering.

You don't install R3 usually. It is for VPP on pin 1, to support EEPROM/EPROM devices that have a VPP pin. These are all old devices that aren't made any more, but you can still buy used and new-old-stock. Don't install R3 if you're using the SST39SF010A part in the BOM linked above, or any 29 or 39 series flash chip. But if you happen to already have a 28F010, 28SF010, 27SF010, 27C010 etc, you can use it instead of the 39SF010, and if so, you need to install R3. 47K the same as the others.

Programming

Requirements:

  • eprom programmer, such as TL-866

No matter which chip or which package type you use on the board, when the jumper is in the PROGRAM position the board provides a pinout on the DIP legs that matches the PLCC version of the chip.

To program the chip,

  • Move the jumper to PROGRAM
  • Put the board into a programmers' ZIF socket as if the whole board were a DIP chip
  • Tell the programmer software that it is the PLCC version of whatever chip is soldered on the board
 minipro -p "SST39SF010A@PLCC32" -w 831000-438-y2k.bin

Install

Move the jumper to RUN

Put the board in the ROM0 socket in the PC-8300

leave pins 1, 2, 31, 32 outside the socket, pretend the white silskreen line is the pin-1 / pin-28 end of a dip-28 chip.

Press Shift-CTRL-Reset to hard-reset the PC-8300 to force it to load the new rom, including re-reading the one-time power-on defaults. If the date says 2000, then you got it. If the date says 1983 or 2083, then you didn't do a full reset.