3.3v operation

mwf · Joined: 06 Oct 2006 Posts: 27 Location: Boulder, CO

Will the ZBasic micros operate at 3.3V? If not, can you tell me which parts prevent this - maybe I can find a substitute.

spamiam · Joined: 13 Nov 2005 Posts: 665

dkinzer · Posted: 17 October 2006, 20:14 PM Post subject:

I have run the ZX-24 at 3.3V for extended periods of time with no observed problems. Nonetheless, this is outside of the specifications for the ATmega32 chip whose operating voltage is specified as 4.5 to 5.5V. The ATmega32L chip, which has an operating voltage of 2.7 to 5.5V, could be used but it has a maximum speed of 8MHz. The remaining components are specified to run at 3.3V. The "space" level for Com1 out would probably be around 3 volts, possibly a problem in a noisy environment or with a longer serial cable.

If you are interested in a low-voltage version we could build a special version of the VM to run at 7.373MHz. An alternate strategy is to select AVR chips for their ability to run at 3.3V/14.75MHz and we can program them with the existing VM.

mwf · Joined: 06 Oct 2006 Posts: 27 Location: Boulder, CO

The question comes up because I have other chips that must run at 3.3v and I could avoid level translators with a 3.3v Zbasic chip. I won't have much volume so doing something too special doesn't make sense. Maybe cherry picking some parts that work is the way to go. The ZX24a might be a better choice with the extra RAM. Have you tried it at 3.3v?

The serial port is going to be connected to a local FT232R so the 3v level on the RS232 should be ok. Bypassing the RS232 signal conditioning and going straight to the chip, like the ZX24ae, would certainly work. Nice of FTDI to allow individual selection of polarity on each pin.

stevech · Joined: 23 Feb 2006 Posts: 657

By RS232, you really mean the serial port data at logic levels, right? RS232 is the name of the standard for the +/- 6 to 12V.

mwf · Joined: 06 Oct 2006 Posts: 27 Location: Boulder, CO

Actually I mean the pseudo RS232 interface on the ZX24. It likely would work with a 3.3v logic level directly to the FT232. The logic level interface at the microprocessor as available on the ZX24e or by hacking the ZX24 is sure to work with 3.3v logic. OK?

stevech · Joined: 23 Feb 2006 Posts: 657

I'd expect (but guessing) that it would work at 3.3V as long as the data polarity is correct. Sometimes an inversion is needed because RS232 drivers/receivers invert as a pair.

mdown · Joined: 03 Feb 2006 Posts: 62 Location: Dallas, Texas

We have been running atmega32's ZX24's at 3.3v for over a year now without any problems. We have started using the ZX44A's as a replacement using the same voltage. One thing to note, the atmega644V versions of the cpus are rated for 2.7v-5.5v. Don do you use the atmega644V part or the plain atmega644?

-MikeD

dkinzer · Posted: 19 October 2006, 14:49 PM Post subject: Re: 3.3v

mdown · Joined: 03 Feb 2006 Posts: 62 Location: Dallas, Texas

Why is it that the cpu wants higher voltages for higher frequencies?

-MikeD

stevech · Joined: 23 Feb 2006 Posts: 657

interesting big picture question - as in the PC CPU Chips, the core voltage is going down as speeds go up! I think the latest run at 1.8V.

Relationship to the FCC Part 15 radiated emissions regulations may come in to play as well - hence this move to dithered clocks to spread the energy out in the spectrum to fudge through the FCC certification compliance.

GTBecker · Joined: 18 Jan 2006 Posts: 457 Location: Cape Coral

> ... the core voltage is going down as speeds go up!

Fewer electrons to move.

Tom

mwf · Joined: 06 Oct 2006 Posts: 27 Location: Boulder, CO

spamiam · Joined: 13 Nov 2005 Posts: 665

stevech · Joined: 23 Feb 2006 Posts: 657

I worked with ECL family chips long ago. They got their speed with high current, not voltage.

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