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> I/o Expansion Of 16f877a, I want 50 I/O pins from a 16F877A
kasuncharya
Posted: January 26, 2012 03:03 pm
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For my project I want around 50 I/O pins, how can I expand I/O pins.
As I know it can be done I2C or 74573 latch IC.

If somebody have experience of this matter please publish diagrams and codes (I use MikroC).

I want to drive 7 stepper motors, dual line LCD module and one port for Inputs.
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Sch3mat1c
Posted: January 26, 2012 04:58 pm
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At what bitrate??

Back in the day, 8255s were used. These have a parallel bus, typical of microprocessors but not microcontrollers. There should be tons of serial (I2C, SPI, etc.) devices on the market that'll do what you're looking for. Run a search at your favorite distributor and see what's available. As for diagrams and codes, you'll find all the data you need in the datasheet.

Tim


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millwood
Posted: January 26, 2012 05:37 pm
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QUOTE
how can I expand I/O pins.
As I know it can be done I2C or 74573 latch IC.


you pretty much answered your own question.
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Village Idiot
Posted: January 27, 2012 02:20 am
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In the very simplest terms:
For inputs, use a parallel in serial out shift register.
For outputs, use a serial in parallel out shift register.
Cascade as many stages of each type as necessary.

As for part numbers, there are hundreds to choose from, depending on requirements for speed, voltage/current rating, number of bits, etc.

In one application, I used a single 32 bit serial in parallel out shift register to drive 32 high voltage (60V) outputs.
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Gorgon
Posted: January 27, 2012 01:39 pm
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You should use the SPI module, to drive serial-to-parallel I/O. Parallel loaded shiftregisters for inputs and latched shiftregisters for outputs. If you do it right, you can read the inputs at the same time you set the outputs.

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