rsmith and I had been discussing that the past couple of weeks. I plan to just make one, and see how much it costs. The PLCC plug-in doohickey is always the problem, the cheapest I can find is 30USD (qty one, small discounts for more). My plan is minimum 8Mb, using a CPLD for LPC emulation and any one of the various cheap USB microcontrollers for interface. I will also add port80 decode and display for myself. I'll keep in mind the suggestions given here, they could be added later pretty easily (with more cost) What I have seen so far:
Parallel ROM emulation (with DIP pins to go with it) Parallel ROM programming LPC ROM programming NVRAM storage of the ROM data device emulation (which could be extended to making the thing into a little logic analyzer for the LPC bus)
The big hazard to this is that SPI is going to take off as the boot source soon (it is in most modern southbridges already). Talking SPI is not a problem, but the ROMs are all going to be soldered down, so running in emulator mode takes on a whole new level of pain. This project is doomed to quick obselence.
When done, I would open the design fully, so anyone could build one, or modify it to their heart's content.
Please reply to me how many of these things you would buy for $50. $75?
Thanks, Tom
On 10/24/06, Peter Stuge stuge-linuxbios@cdy.org wrote:
On Tue, Oct 24, 2006 at 12:30:01PM -0700, Lu, Yinghai wrote:
Hope someone build one USB rom emualator for openmarket.
What is the minimum useful size? Would 2Mbit be enough? Can anyone suggest a reasonable target price?
A USB micro, SRAM and some mux chips is really all that's needed. Maybe even use flash in the emulator. But to have an upgrade path and best configurability would probably require a PLD. (So that one hardware can do both LPC and parallell, and maybe even 3V3 but still be 5V-tolerant.)
//Peter
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