Hi and some Questions

Tom (SA)

Hi There,

I'm a newbie to this forums and to parallax products. I've been introduced to the propeller when I got myself a ybox2. So far I managed to create my own little propserial programmer and done minor changes to spin programs and loaded them onto the ybox. But next up I want to create my own little prototype board (I'm still planning to order a development board + prop plug, but it usually takes 4 weeks to get here in SA). From what I can gather in the schematic for the propeller demo board, I need to wire up a propeller with the eeprom.

(1) Does it have to be a 24LC256? I currently have a 24LC32. Can I use that instead ?
(2) Schematic shows a 5Mhz crystal, is that required ? Isn't there an internal oscillator of 80Mhz ?
(3) Any other parts I need to have to create a small working setup ?

I've got a project idea that I also want to turn into a contest entry for the propeller. This will be my first project so I hope I'm notrying too much too fast.

Spork Frog

1. AFAIK, no. The EEPROM must be at least 32K in size (IE 24LC256, 24LC512, or 24LC1024). This is because on bootup, the Prop bootstrap reads the first 32K of the EEPROM and copies it all into Hub RAM. I think that anything smaller would cause errors which may or may not be handled. Best case, it works with the small amount of space it has. Worst case, it doesn't boot.

2. A crystal is required for operation at 80MHz. There is an internal oscillator that runs at 12MHz.

3. Partswise, just the voltage regulators and caps, I believe. Plus power switch and reset circuitry.

Leon

You only need one voltage regulator, of course, if the whole system is 3.3V.

Leon

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Tom (SA)

Spork Frog said...
1. AFAIK, no. The EEPROM must be at least 32K in size (IE 24LC256, 24LC512, or 24LC1024). This is because on bootup, the Prop bootstrap reads the first 32K of the EEPROM and copies it all into Hub RAM. I think that anything smaller would cause errors which may or may not be handled. Best case, it works with the small amount of space it has. Worst case, it doesn't boot.

2. A crystal is required for operation at 80MHz. There is an internal oscillator that runs at 12MHz.

3. Partswise, just the voltage regulators and caps, I believe. Plus power switch and reset circuitry.

(1) hmm, but isn't the 24LC32 a 32k eeprom ? And the 24LC256 a 256k eemprom ?

(2) Only 5Mhz, or can it be other sizes as well ?

(3) Yup, I've got those [noparse]:)[/noparse]

Thanks for the help

Tom (SA)

nevermind the question, just figured it out. The 32k is 4k * 8 pages. I found a 24LC1025 in my box as well, is there an advantage of using a 24LC1025 over a 24LC256 ? More space for a bigger program ?

Mike Green

1) The number after the 24LC is a bit count, not a byte count, so a 24LC256 is a 32K byte EEPROM

2) The crystal can be anywhere in the range 4-8MHz as far as the crystal oscillator is concerned. The PLL (phase locked loop) multiplies this by 16 and feeds the result to a divider. There are taps at x16, x8, x4, x2, and x1. Officially, the PLL is only guaranteed up to 80MHz over the full temperature range and full power supply range, but people have successfully used 6MHz crystals for a PLL frequency of 96MHz.

The Propeller Tool ignores any EEPROM over 32K bytes, but several programs allow you to store programs and data anywhere in the EEPROM. FemtoBasic is one example. You can copy programs from the base 32K to other 32K "pages" (and run them) and you can store Basic programs above 32K in any attached EEPROM. There are Basic statements for reading and writing anywhere in EEPROM.

Post Edited (Mike Green) : 8/2/2008 7:09:01 PM GMT

hippy

Watch out for 24LC1025/24AA1025 and larger because some (all?) of those need A2 connecting to +V so they won't work as drop-in replacements for Propeller Boot Eeprom.

Spork Frog

@Mike Green: To be fair, you can use a 10Mhz crystal and PLL x8.

Mike Green

Yes, I'm sorry. It's the system clock frequency that's only guaranteed to 80MHz. The PLL can run faster than that, up to 8MHz x 16 = 128MHz as far as I remember.