On Mon, May 7, 2018 at 9:08 AM, Diggy Dude <[email protected]> wrote: > Thanks, Fugu! > > So the modern solution is a single SRAM and capacitor on a SOIC-to-DIP > breakout? What's the RAM chip they're using?
and a logic chip (there're a few different approaches here) to combine the separate chip selects to a couple of addresses and a single select signal. My own version of the circuit uses the fewest ports possible (at least if nobody comes up with a different approach I couldn't think of). The RAM chip must be a CMOS static ram, 8kx8 and with low power standby (not all have this feature). The original 8k modules were specified for 4 uA max standby current, that allows the standby battery to keep the RAM content for over a month. Usually the suitable chips have L or LL in the part number, but you better check the datasheet for the fine details. Most of the suitable RAM chips have a measured standby current of 0.1 uA (often less) at 3.3V if the chip select are driven with the correct voltages. At these current levels, cleaning the soldering flux is a must. I've measured up to 15 uA of standby current on badly cleaned modules. YMMV. Glue logic *must* be 74HC family, it has a suitable current draw at 3.3V standby and suitable speed. In one case I've used 74AHC and it worked well too. > > -- Jim > > On Sun, May 6, 2018 at 10:29 PM, Fugu ME100 <[email protected]> wrote: >> >> You could try >> https://www.arcadeshopper.com/wp/?page_id=11#!/8k-RAM-module-for-Model-100/p/104430801/category=28313042 >> >> They have the M100 modules if you want to buy. >> >> If you want to build your own there are PCBs on OSH Park for surface mount >> and DIP versions. >> >> No need for any pillaging :) >> >> From: M100 <[email protected]> on behalf of Diggy Dude >> <[email protected]> >> Reply-To: <[email protected]> >> Date: Sunday, May 6, 2018 at 8:13 PM >> To: <[email protected]> >> Subject: [M100] 8K RAM module >> >> Anyone know where I can get an additional 8K for my 24K M100 without >> pillaging another M100? Let's face it: if I got another M100, I'd be >> inclined to leave it intact. > >
