Re: TI-H: Parallel Memory expansion
[Prev][Next][Index][Thread]
Re: TI-H: Parallel Memory expansion
Mel Tsai wrote:
>
> The Expander II and III are both in development right now, and should
> be available within a few months.
>
Cool; I hope whatever I build will have it's own niche though. :)
>
> Yes, there are two new places that are selling high capacity serial
> flash EEPROMs but neither are easy to interface to and neither are
> compatible with the current schematic. There is a two-wire 8Mbit
> flash chip coming out in like 5 months from this place, but I probably
> won't use it if it's expensive. The others are all SPI bus which
> means a minimum of 4 wires are needed (5 or 6 are preferred), whereas
> the TI only has 2. That is why a microcontroller is the easiest way
> to go, and it also allows you to do a lot of cool stuff :).
The schmatics I've seen need 3 wires, a Clock, data, and the ground,
which the TI-85 can do just fine.
And I must disagree on your opinion about Microcontrollers. A
Microcontroller such as a PIC is unable to address memory, which equates
to a large amount of code. And who has the equipment to program a PIC
microcontroller? Other controllers, such as the Z182, used by one
expander require more external circuitry, and is itself more powerful
than the system it would be "serving".
> And yes, the new expanders will probably still be using serial flash
> EEPROM chips since they are convenient to access and have low
> pincounts (these upcoming ones are cheaper, too). Using a parallel
> eeprom, while technically more prevalent in the semiconductor market,
> are significantly more difficult to access because an 8Mbit parallel
> EEPROM requires over 32 chip connections (8 data lines, 20 address
> lines, minimum 4 control lines)! That makes for a very complex
> printed circuit board even with a microcontroller.
Detailed/Computer aided design of the PCB can help keep the placement of
parts simpler. Also, I plan to sell pre-etched PCB boards (Perhaps with
the Surface Mount FLASH chip soldered on allready.) So the person can
solder the simpler DIP chips and connect the cables, etc.
I'm not really arguing for either side, they both have drawbacks, I'm
just saying that Parallel FLASH chips can be used without the need for
microcontrollers.
Follow-Ups:
References: