Underclocking ARM and SRAM

I have an LPC3180 header board that needs 10MHz+ crystals to run per spec. I plugged in a ~2MHz crystal and it ran, as slow as expected.

I've underclocked PIC parts down to being static, even using a button as a clock. Can this be done with ARM MCUs? Can this be done with ARM MCUs interfaced with SRAM chips?

Reply to
ghazanhaider
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Read the datasheet - there should be a min clock freq spec - if this is 0 Hz, it will work! SRAM certainly won't have a problem.

Reply to
Mike Harrison

it will work!

For an external crystal, the LPC3180 accepts from 1 to 20 MHz. It also has an internal 32.768KHz oscillator, which can drive the system clock at 13 MHz via a PLL.

--Gene

Reply to
Gene S. Berkowitz

Hz, it will work!

Oops! I meant an LPC2138. Its minimum per user manual and datasheet is

10MHz.

I've been keeping an eye on the lpc3180 and its been on my mind. Samples arent out yet.

Reply to
ghazanhaider

Interesting. I wonder why it's minimum is higher than other members of the family (such as the 2106)?

Robert

Reply to
sub2

I dont know but I intend to play with much lower frequencies. Maybe its for the DAC and UARTs, I wont need em. Maybe ISP wont work. But last I tried a blinky prog 2MHz worked great. Crystal I mean.

Reply to
ghazanhaider

As I recall, on the other members, the UARTs worked fine (not surprising) but ISP expected 10MHz or better. The big issue was the PLL which required a minimum of 10MHz input.

Maybe the ADC has some timing limitations (Maybe hold time on the S/H?) but I would have thought the DAC to be all right.

Robert

Reply to
sub2

Well, I'm aiming for a really low power system, and will start testing underclocking the lpc2138 first. The pll divider only takes me to about

1MHz or a little less... but if the 2MHz crystal test worked so should possibly a 32KHz. In the longer run I have the lpc2888 in mind, but thats a bigger testing rig at 1.8V plus the low power sram and flash. That thing has a 10MHz limit too and its timing with sram and flash will be tricky. Gotta make it work.

Gotta be the first one to make a solar powered linux computer that you can put in your pocket!

Currently I need a square foot of panel in a bright indoor room as a minimum. Aint got pockets that big.

Reply to
ghazanhaider

The datasheet has power consumption numbers down to 0 Hz (on the graph), maybe there is another clock divide down somewhere like on the Atmel ARM's.

Reply to
steve

OK heres an update.

A 2MHz and a 1.8432MHz rectangular crystal both worked, but a cylindrical 32.76kHz crystal failed. With the 2MHz and PLL divider at

16 it will run at 125kHz.

I think I'll go xtal shopping till I find the slowest and lowest power at which it'll work, then I'll do it with the lpc 2888 or lpc3180 (whichever is at 1.8V) for the lowest power.

Reply to
ghazanhaider

Anyody knows where I can buy an LPC3180 development board? I also need embedded linux for it with USB host and HID support, also I need the GNU C++ compiler for it that supports the co-processor built into the LPC3180.

I been looking for weeks cant find none of those.I'm desperate, and need it immediately!

please reply to snipped-for-privacy@islandlogix.com

Thanks

Reply to
smaddy

Wow you must be late on a project. Development always takes its due time.

A development board for the LPC3180 cannot be trustworthy or tested. Since the LPC3180 has never been manufactured and there arent any samples available. I'm impatient for those too, I'll bet philips will just be distributing their first batch as samples.

Start developing with the LPC2880 chips since they should be similar enough (except for ARM7 instead of ARM9). I'm waiting for the Olimex boards which should be next month. Also waiting for their L2290-8M boards.

Even when they're out, you cant have them immediately.

smaddy wrote:

Reply to
ghazanhaider

digikey seems to have them

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Reply to
steve

Hmm, so that Nohau LPC-3000 board sitting on my co-worker's desk running his code must be a figment of my imagination, and the 138 pieces Digi- Key shows in stock must have been something I ate...

--Gene

Reply to
Gene S. Berkowitz

Wow, I stand corrected. The standardics.nxp.com site shows it as planned instead of sampling.

I must not be on their favorite customer list.

Reply to
ghazanhaider

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