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Cheap digital logic?

So, I have this algorithm. It's pretty simple. It works well on an MCU, which is fine and all, but if I could make it cheaper by using ICs instead, that'd be cool. This is mostly academic.

Basically, I need 64x12*2 bits of memory. That's 2 banks of 8x8x12 bits. Each bank is one "buffer". While an external circuit is writing to one, this circuit will be reading from the other.

So I'll need something that can select which bank the circuit is reading from, as well as the external circuit is writing to.

I need a "clock" or "timer" that runs at about 60KHz

I need at least a 10bit counter.

The lower 3 bits of the counter control which "row" I have selected on a

1-of-8 demuxer.

The next 3 bits are control which column to read from in the buffer. (buffer address basically the lower 6 bits).

For each of the three nibbles at that address, I compare that magnitude to the high 4 bits of the counter. The result of that comparison is then pushed into a shift register (one register per nibble).

Now, the full circuit needs the shift-registers and demuxer, regardless of whether or not I use an MCU, so those shouldn't factor into the price, unless there is a counter where the lower 3 bits are pre-decoded.

An MCU with enough processing power and memory costs < $1 (about $0.67 for the SOIC package). Can I do this cheaper with non-MCU parts?

I haven't been able to find a way, but I'm not entirely sure what I'm looking for.

Thanks, Daniel.

Reply to
Daniel Pitts
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This sounds trivial in a CPLD or maybe a small FPGA (with the RAM being the key). Probably about $10 in small quantities. Depending on your skills, getting a package you're comfortable with is probably the biggest issue in selecting a part.

Reply to
krw

That doesn't sound cheaper than a $1 MCU ;-)

Reply to
Daniel Pitts

Neither does unit logic or the board space to put it on. ;-)

Reply to
krw 

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No.
Reply to
John Fields

Good answer. It is what I had come up with on my own, but wanted to hear from more experienced people first. Thanks.

Reply to
Daniel Pitts

$0.90 from DigiKey in onsies:

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I didn't check to see if it's big enough for what the OP wants, though. I suspect that he could find something for under $2.00 in qty 1, but if his application is slow enough it's still probably more sensible to go with a micro.

It's not like there's jelly-bean 7400 series memory parts available any more, and if there were you'd need a wad of parts around them to make it all work -- this is why CPLDs were invented in the first place.

--
My liberal friends think I'm a conservative kook. 
My conservative friends think I'm a liberal kook. 
Why am I not happy that they have found common ground? 

Tim Wescott, Communications, Control, Circuits & Software 
http://www.wescottdesign.com
Reply to
Tim Wescott 

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You're welcome. :-)
Reply to
John Fields

I didn't look at all, but he's going to need some RAM. Block RAM will probably do it, but it's not going to be the smallest device.

74HCxx is still available but he's not going to save any money. I agree with the CPLD comment, though some CPLDs aren't going to have memory devices. Using a LUT per bit is going to get expensive.
Reply to
krw

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