Shift Registers and the Prop..
RingWorks
Posts: 5
Greetings! My first post so don't be to tough on me...
I am researching the I/O capabilities of the Prop to work with 4094 IC's (8 bit) in a shift and store bus register solution. Basically, I need to have 96 I/O ports for output and 96 I/O ports for input. I am going to use 4094's in series to achieve the needed amount of ports. I would like to do this with a 16 bit IC if possible and will be putting together some test boards in the next few weeks. Any tips towards helping with this endeavor would be appreciated.
David
I am researching the I/O capabilities of the Prop to work with 4094 IC's (8 bit) in a shift and store bus register solution. Basically, I need to have 96 I/O ports for output and 96 I/O ports for input. I am going to use 4094's in series to achieve the needed amount of ports. I would like to do this with a 16 bit IC if possible and will be putting together some test boards in the next few weeks. Any tips towards helping with this endeavor would be appreciated.
David
Comments
Parallax sells and supports the 74HC595 for serial output expansion and the 74HC165 for serial input expansion and has lots of examples of their use with the Stamp in their various tutorials. They, like the 4094, are 8-bit devices and are usable in series.
Philips and Microchip make a 16-bit I/O expander with bidirectional I/O pins (MCP23017 for I2C and MCP23S17 for SPI) that works very nicely with the Propeller. The MCP23017 can be daisy-chained (up to 8 devices) off the same pins as the boot EEPROM.
http://www.allegromicro.com/en/Products/Categories/ICs/vfdisplaydriver.asp
I have· not used them but look pretty simple. THe shiftin and out should work with them.
Jim
To answer your questions :
Why the 4094? - Because it can be used in series to accomplish the I/O requirements that I am looking to meet. The cost of the chip is .38 vs $1.77 for the 74HC595.· I am very new to microprocessor developement, honestly I have not looked at the 74HC595 in depth enough to fully appreciate the features that it offers that would be an advantage over the 4094.· There might be a speed advantage in that the 74HC595 cycles data a little diffrently then the the 4094.· Ultimately, if the end result is that I/O communications can occur within milliseconds using a 4094 at·1/4 the expense of the 74HC595, then I will go with the 4094.
What do you mean by a 16 BIT IC?·- 16 bit path intergrated circuit
I need a total of 96 inputs and 96 outputs (and more in some cases) not bidirectional.
The Philips and Microchip chips sounds very promissing however·I have not found them in quantities less then a 1000.· I will see what I can find for the MCP23017, I just need an intergration example to work from..
Jim - Coolness, I will take a look at it.
Post Edited (RingWorks) : 5/1/2007 3:58:22 AM GMT
Leon
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Amateur radio callsign: G1HSM
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I like using 595's because they are very easy to use, and quite flexible.
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Graham
Bill - Good call! Thanks, I will take a close look at the 74HC595's and see how they stack up against the Allegromicro A6818 for what I am wanting to do.
Graham - I am sure Mike knows what a 16bit IC is too, me being the new guy on the block, I just answered the question strait up. Doh!
I would rather use a 16bit ( or a 32bit chip for that matter ), because the board design would require less chips to be used in total. The cost involved is a factor, but if the cost is negligible, then a larger chip, 16 or 32 would be better the 8. I need to control 43v and 5v devices with these chips, either through the use of a Darlington transistor or directly if the chip can handle it. Allegromicro has a 32 bit chip that looks very promising. Their A6818 can handle output at 60v, with 3 chips I could get the output I need for 96 devices. The Allegromicro A6818:
http://www.allegromicro.com/en/products/part_numbers/6818/ runs about 5 bucks, because I would not have to use transistors to control higher voltage devices that is a huge advantage. I might be missing something here though, I certainly could use any insight the community is willing to offer.
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Paul Baker
Propeller Applications Engineer
Parallax, Inc.
Post Edited (Paul Baker (Parallax)) : 5/1/2007 4:17:05 PM GMT
Since the chip can handle clocks up to 30MHz or so, it should be fairly fast to load, even for 100 bits (over 100K/sec refresh).
If you don't need refresh rates over 200Hz, you could do the whole thing in Spin, otherwise you'll need an assembly routine.
Is this for a musical application?
Post Edited (Skogsgurra) : 5/2/2007 5:00:01 AM GMT
Pete