Hobby project.. please help me choose the right CPU

[calamari]

Hi,

I'm hoping to create (for a hobby project) a small portable programmable device / clock that has minimal power requirements so that it may run for years on a single battery. I'm willing to sacrifice clock speed as much as possible to attain my goal of a long running time. I still have a lot to learn, but I wanted to at least start with the right CPU.

Can you recommend a CPU based on the following requirements?

* As low a power requirement as possible. Must be static so I can choose a clock speed. My power source will be a single CR1616 (3v, 57 mAh) lithium battery. I would like the CPU and RAM to be able to be powered for years off a single battery. This low-power requirement is essential to my project.

* Clock speed is NOT important, but I would like to be able to vary the clock speed. I've read about a static design where the CPU can be stopped, then woken when needed, I'd like to be able to do that to save power.

* Less than $30, if possible. I only want to have to buy one.

* DIP option so I can build it on a breadboard. Either that, or a package type that has an adapter to DIP.

* Needs to be able to reprogram itself while running.. this means I need to be able to run my code from RAM as well as ROM (I have an EPROM burner). The reason I bring this up is that I've seen PIC processors with built in flash (which is cool) that require that programs must be run only from the flash. This means that programs can't be run from an external RAM (this is bad, because then I can't program the device while it's running).

* If there are support chips required, they must also be very low power, etc.

* Here is the I/O I'll be doing: serial I/O (RS-232), some kind of low power LCD display, some kind of keypad, 60hz (regular) clock, maybe a speaker or buzzer. I still need to learn how to work with I/O, but I've seen some CPU's that include some of these features (such as serial I/O), which would be nice. It's important that I not have to run the chip at full speed to maintain my clock accuracy, though.

Thanks a lot for your help,
Jeff

[calamari]

I was looking more closely at some of the other posts in the forum and realized that I've probably asked my question at the wrong website. I just looked at the title "CPU World", and made a bad assumption. I'm sure that I can find a decent CPU for my project. I've found the Intersil 80C86/8, which is a CMOS version of the CPU used in the original IBM PC. It has a static design so that the clock is stoppable, and I'm familiar with programming it. I'm still hoping to find a more recent CPU because maybe it'd be faster or have more features for the same power usage.

If I'm understanding the site correctly now, it seems posts are about ID'ing chips and the such for the purposes of building a CPU chip collection. Someone with a huge chip collection wouldn't necessarily know anything about what the chips did or what their strengths and weaknesses are... I'd guess you guys are great at telling what all the marks and dates and variants of a CPU are, though. For me, using the CPU to do something is the cool thing. But, hey, I'm a programmer.

So, I apologize for my off topic post. To bring it more on topic, my favorite CPU is the Fairchild F8 in my Channel F console (from Wikipedia):

* CPU chip: Fairchild F8 operating at 1.79 MHz
* RAM: 64 bytes, 16 kilobytes VRAM
* Resolution: 128 × 64 pixels, 102 × 58 pixels visible
* Colors: eight colors (four color max. per line)
* Audio: 500 Hz, 1 MHz, and 1.5 MHz tones (can be modulated quickly to produce different tones)
* Input: two custom game controllers, hardwired to the console
* Output: RF modulated composite video signal, cord hardwired to console

"The F8 was so early that the process technology of the era couldn't fit all the needed circuitry onto a single chip, and the F8 was in fact a "family" of chips that had to be wired together to form a complete CPU."

One thing that article doesn't mention is that those 64 bytes of "RAM" are actually 64 internal registers. I'm very impressed by what they were able to accomplish with such a limited system. I especially like Channel F Baseball and their unique Dodge It game.

Jeff

[CPUShack]

You're going to be hard pressed to run everything off of that battery, especially serial as it is power hungry.

I would reccomend aPIC series processor if you can find one that works with what you want.

If not look at the any MCS-51 MCUs available. They have many features now and most are fully static cores.

The instruction set is similar to 8086 so programming wouldnt be hard.

(I prefer to program them in C myself)

[gshv]

You need a microcontroller for your project, not a CPU. While Intersil 80C86 CPU has static design, you still need to add RAM, ROM and I/O peripheral to achieve something that you can do with one microcontroller. Many people in this forum deal with CPUs and don't care much about microcontrollers, that's why you didn't get any response to your first post.

If you didn't have that EPROM requirement I'd say take a look at PIC (www.microchip.com) or 8051 (for example http://www.atmel.com/dyn/products/param_table.asp?family_id=604&OrderBy=part_no&Direction=ASC) microcontrollers.

Gennadiy