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crgwbr
01-21-2008, 01:33 AM
If my thinking is correct, the Hydra has an onboard eeprom that the Prop can boot from. However, if you put in a program card, it will boot form that instead. How does this work? I'd like to incorporate a similar design into a board of mine, but I can't seem to figure out how to accomplish that.

Regards,
Craig

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I have a duel boot of Ubuntu Linux and Windows Vista. Vista, because it came with the PC, Ubuntu because I like software that works.

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Mike Green
01-21-2008, 02:32 AM
The Hydra manual describes this. Basically, the expansion card circuitry uses the address select pins on the EEPROMs which set what addresses the EEPROM will respond to. The on-board EEPROM is set so that one of the address pins is pulled down to ground when there's no expansion card. When an expansion card is inserted, there's a jumper to Vdd that pulls up the address pin. The EEPROM on the expansion card has all its address pins connected to ground. When there's no expansion card, the on-board EEPROM appears in the 1st 128K of the EEPROM address space. When an expansion card is inserted, the on-board EEPROM appears in the 2nd 128K of the EEPROM address space and the expansion card EEPROM appears in the 1st 128K of the EEPROM address space.

deSilva
01-21-2008, 02:57 AM
128K is not a typo .. The Hydra comes with a 24C1025 http://forums.parallax.com/images/smilies/smile.gif The enclosed schematic shows what Mike explained. Note BTW that most EEPROM's A0..A2 are internally pulled down, so the resistor (or the common Vss bind) is not strictly necessary.

crgwbr
01-22-2008, 02:57 AM
I'm guessing that this (http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/txtSearch/eeprom/List/1/ProductID/453/Default.aspx?SortField=ProductName%2cProductName)e eprom is the 128k eeprom that the Hydra uses. I can't find any information on it. Does it have the same pinout as the 32k eeprom that is standardly used by the prop?

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My system: 1.6 GHz AMD Turion64 X2, 4GB DDR2, 256MB ATI Radeon Graphics card, 15.4" Widescreen HD Screen

I have a duel boot of Ubuntu Linux and Windows Vista. Vista, because it came with the PC, Ubuntu because I like software that works.

"Failure is not an option -- it comes bundled with Windows."

Use The Best...
Linux for Servers
Mac for Graphics
Palm for Mobility
Windows for Solitaire

Mike Green
01-22-2008, 04:23 AM
Find the datasheet for it. That's the only way to make sure of the details.

crgwbr
01-22-2008, 04:26 AM
I tried finding the data sheet for it but i
crgwbr said...
can't find any information on it.
Nevermind though. I found a 512k eeprom at mouser, i'm going to use instead.

Thanks anyway,
Craig

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
My system: 1.6 GHz AMD Turion64 X2, 4GB DDR2, 256MB ATI Radeon Graphics card, 15.4" Widescreen HD Screen

I have a duel boot of Ubuntu Linux and Windows Vista. Vista, because it came with the PC, Ubuntu because I like software that works.

"Failure is not an option -- it comes bundled with Windows."

Use The Best...
Linux for Servers
Mac for Graphics
Palm for Mobility
Windows for Solitaire

Post Edited (crgwbr) : 1/21/2008 9:31:39 PM GMT

deSilva
01-22-2008, 06:16 AM
That is fine.. all have the same pinout, which is easy with I2C chips...