[Coco] 128K/256K EEPROM Cartridge board

[Mark J. Blair]

> On Jan 25, 2015, at 14:41, Chad H <chadbh74 at hotmail.com> wrote:
> 
> I have the OE# and CE# tied to the cartridge CTS.  This is the same we did for the 2764 and 27128's, etc.
> 
> Does this need to changed for writing to the chip?

Yes. OE# and WE# may not be pulled low simultaneously. Pulling down OE# tells the chip that it should drive read data onto the data bus, while pulling WE# tells it to accept data driven by the CPU onto the data bus. Driving both low simultaneously will result in bus contention.

I have not put much thought into this or even looked at a datasheet, so you will need to do some research, but my first thought after a cursory glance at my old CoCoEPROMpak schematic is that WE# would be driven by R/W# from the cart slot, CE# would be driven by CTS# from the slot, and OE# would be driven by an inverted R/W# signal. So you would need to add an inverter, such as a single-gate 7404. I might be talking out my butt, though, so please think before paying for boards. :)


-- 
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/