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how to interface 28 I/O ports with PC?

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28 I/O ports ?

Hi!

Any idea how to build some PC interface (via rs232, paralel port or ISA/PCI card) with 28 I/O lines or maybe some MCU with 28 I/O ports ?
Need to control 7 BCD coded slots .

Thanks !
 

Here are some ways:
1. There are a lot of 51 uC with 4 8-bits ports, like Atmel 8252. Also, PICs in 40 pins package will work. It is better to use SPI software emulation through the parallel port to connect them.
2. You can also use simple CPLD from Xilinx or Altera. They have enough pins to be connected to parallel port.
3. You can use cheap network PCI card to re-design it to a simple PCI IO card. After that you'll get a plenty of resourses for IO.

Cost of all these solution is about 5-7 $.

Hope it will help!

Ace-X.
 

Or you can use these old things 8) called 'latches' (74x373 or 74x374)
There are 8+4 pin usable in output on the parallel port

With 4 latches, it takes 4 pin two drive the latch, and 8 bits of data.

=>32 ouput
 

You can connect more latches with decoder chip. And use 64, 96 or more output. If you have bidirectional parallel port you can use ports as input too.
 

The MCU from fujistu have enough I/Os .
9x8 !
The MB90540 serias.
 

You can wire two 8255 to printer port and got 48 IO pins. Connect one 8255 does not need any extra logic chip if you accept 24 IO.
 

Thanks to all answers !

I find PIC 16C74 very interesting with 33 I/O pins !

**broken link removed**

(in german)
 

As my experience, 8255 was not robust.
You may check TTL IC (LS244 or something).
 

Bat said:
Or you can use these old things 8) called 'latches' (74x373 or 74x374)
There are 8+4 pin usable in output on the parallel port

With 4 latches, it takes 4 pin two drive the latch, and 8 bits of data.

=>32 ouput
Click to expand...
only '373 is latch, '374 contains 8xD (it's not the same, but can be used interchangeably in many cases)
better to use 573 or 574 - this have more "friendly" pinset.
 

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