Crap I'm sorry Mike! But the question was about an option rom not the main rom. A dip28 chip just about fills all available volume in the option rom socket. If you need to add anything else to the board, it will be difficult. There is a little room on the edge, and there is about 1/10" of height across the bottom. Can you make a 27C256 both usable and re-programmable within those constraints? Would it need a jumper and resistor like 28C256 does?
As for rex, now that Stephen has put a version of rex up on osh park I plan to try to build one and we'll see. I've already ordered a set. If it costs more in parts, that's a potential reason. If it's more difficult to build, then that is a potential reason. It was easy to do the soic option rom, and the through-hole plcc socket main rom, and your own dip28 main rom. The qfp legs are finer than soic, but still look doable, but that tsop chip...well we'll see, maybe it's fine. If it requires special software or hardware to program the cpld, that is a protential reason. I can program an eprom using small purely open source software and $30 hardware. For the fpga in the MISE, I got a ByteBlaster for $25 and the programming software was free, but it was a large download of proprietary software, and was not easy to get working on the linux netbook I like to use for stuff like this where possible. I don't know yet what it takes to program the cpld on the rex, but I'm guessing it will be doable and within reason like those examples. If there is any software incompatibility, that is a potential reason. If it conflicts with the option rom socket, then that is a potential reason. On Jun 15, 2016 10:41 PM, "Mike Stein" <[email protected]> wrote: So it's become *Stephen's* M100ROM board now? ;-) I don't see any reason myself why you couldn't make a re-programmable Option ROM adapter using a 27C256 EPROM but I'm not going to get into another discussion; I am curious though why, with the various other options including REX, you'd want one? Personally, I still think an Option ROM adapter using a RAM chip would be nice; I wonder if the FigTronix one could be adapted... m ----- Original Message ----- *From:* Kurt McCullum <[email protected]> *To:* Model 100 Discussion <[email protected]> *Sent:* Tuesday, June 14, 2016 2:30 PM *Subject:* Re: [M100] Adapter Board Thanks for all the information. The list is once again a wealth of knowledge. I'll look into the other boards. Kurt On Tuesday, June 14, 2016 10:18 AM, Brian White <[email protected]> wrote: A 27C256 is problematical in the option rom socket because you can't reprogram it once you solder it. Or at least it would be pretty hard to squeeze the couple extra components to handle the Vpp pin so that it is tied to Vcc (or gdn or no-connect, I forget what it needs right now, other than that it should *not* be connected to any of the socket legs) during normal run-time operation, but not tied to Vcc and instead *is* routed to an edge contact for programming. The 28C256 board can do it because the chip is SOIC package and there is physically room for the parts. There is no such thing as a SOIC 27C256, or at least not an erasable one. Burning and soldering a chip as a one-way trip is not really hobbyist friendly. You risk wasting $6 chips and having to de-solder, clean, and resolder chips on the board for every mistake or testing another rom. It's different if you're producing 100 copies of the same thing to sell. You don't care about re-writing then. But in that case you have the resources to just whip up your own new board any time you want. A few different similar board designs are public that you can download and copy, and even the cad software is free (kicad). Edit and upload to osh park and order as set for $6. But I suggest just use the SOIC v2.0 28C256 board. And get the option rom programming adapter v2 at the same time. And some singlenrow machined round pin headers for the programming adapter. Or use the m100 board (Stephen's, not FigTroniX) and use the option rom feature on that. It goes in the main rom socket inside, not in the option rom socket, and it can provide both a main and option rom in one uv-erasable 28 pin dip 27C512. -- bkw On Jun 14, 2016 11:42 AM, "Stephen Adolph" <[email protected]> wrote: ah sorry I missed that. yah it is for main rom socket. not optrom. but it can provide optrom. On Tue, Jun 14, 2016 at 11:35 AM, Kurt McCullum <[email protected]> wrote: > Would it just need to be cut down to fit into a 102 or 200 optrom slot? I > suppose since the 200 has a regular socket for its main ROM it might work as > is. > > > > On Tuesday, June 14, 2016 8:20 AM, Stephen Adolph <[email protected]> > wrote: > > > the M100ROM board supports 27C256.. > > On Tue, Jun 14, 2016 at 10:58 AM, Kurt McCullum <[email protected]> > wrote: >> There have been a few new adapter boards for the OptRom slot of the >> 100/102/200. I notice that none of them support a standard 27C256 EPROM. I >> know these boards used to be available, along with the wrap around >> flexible >> circuit boards used by Traveling Software. Does anybody know of an OSHPark >> design that exists? >> >> Kurt > >
