Author Topic: Altera Cyclone II mini board: why hardwire external pins?  (Read 258 times)

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Offline obiwanjacobi

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Altera Cyclone II mini board: why hardwire external pins?
« on: May 21, 2020, 08:49:11 am »
I am looking at the schematic of a cheap ebay Altera Cyclone II mini board and I am wondering why they chose to short 4 pins (pins: 26, 27, 80 and 81) to 1.2V and GND - pins that also are exposed to the pin headers (P2 and P4)?

Based on the pin documentation of the Cyclone II (T144) they are just normal IO pins (with a differential function)...

I would understand if they would not be used - when there is not enough room on the pin headers to break them out, but that is clearly not the case.

Why?

At this point I am thinking of simply removing those zero Ohm resistors (R1, R2, R9 and R10) to get use out of those pins...
« Last Edit: May 21, 2020, 08:51:27 am by obiwanjacobi »
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Online oPossum

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Re: Altera Cyclone II mini board: why hardwire external pins?
« Reply #1 on: May 21, 2020, 09:10:13 am »
That may have been done to support another part in the same package that does require power on those pins.
 

Online BrianHG

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Re: Altera Cyclone II mini board: why hardwire external pins?
« Reply #2 on: May 21, 2020, 09:14:48 am »
That may have been done to support another part in the same package that does require power on those pins.
Yes, the larger core of the EP2C16/EP2C25 requires more current for their larger core, hence those IOs are changed into VCCint & GNDint.  I hope that board's regulator can handle it if you goto the larger FPGAs...
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Offline obiwanjacobi

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Re: Altera Cyclone II mini board: why hardwire external pins?
« Reply #3 on: May 21, 2020, 09:16:02 am »
Package as in the board or the Cyclone II chip?

Edit: I see you mean the chip.

There's practically nothing on the board.

« Last Edit: May 21, 2020, 09:18:39 am by obiwanjacobi »
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Offline obiwanjacobi

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Re: Altera Cyclone II mini board: why hardwire external pins?
« Reply #4 on: May 21, 2020, 09:24:10 am »
That may have been done to support another part in the same package that does require power on those pins.
Yes, the larger core of the EP2C16/EP2C25 requires more current for their larger core, hence those IOs are changed into VCCint & GNDint.  I hope that board's regulator can handle it if you goto the larger FPGAs...

Only the EP2C5  and EP2C8 come in a T144 so is this a left over of a generic schematic ...?

Seems to me I can safely remove these zero-Ohm R's.
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Online BrianHG

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Re: Altera Cyclone II mini board: why hardwire external pins?
« Reply #5 on: May 21, 2020, 10:29:16 am »
Sorry, my mistake, I quoted the CycloneIII T144 devices.
Yes, the CycloneII T144 EP2C8 has less IOs then the EP2C5 as listed in the CycloneII handbook on page 22.
In the CycloneIIIs, this divide doesn't begin until it's larger devices which are also available in T144.

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/cyc2/cyc2_cii5v1.pdf

In my CycloneIII designs which use multiple generations like this, I usually just wire the VCCints and GNDints and make sure I keep those pins as inputs when compiling for a smaller Cyclone where those pins may be IOs.
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Offline obiwanjacobi

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Re: Altera Cyclone II mini board: why hardwire external pins?
« Reply #6 on: May 22, 2020, 06:07:06 am »
I think I need all the pins I can get on this one  ;D  8)
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Offline james_s

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Re: Altera Cyclone II mini board: why hardwire external pins?
« Reply #7 on: May 22, 2020, 06:14:36 am »
I have about a dozen of these boards and I have always removed the zero ohm jumpers, also the resistor and capacitor that is wired to one of the other pins. I needed every pin I could get for my vector game. I've developed a bunch of projects for that board.

https://github.com/james10952001

 

Offline obiwanjacobi

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Re: Altera Cyclone II mini board: why hardwire external pins?
« Reply #8 on: May 22, 2020, 06:23:18 am »
I left the R/C to act as a reset pin... - but, yeah.

I also hate it when they attach buttons to the pins without R's - an accident waiting to happen.

Attached is a pin planner csv file (as .zip) you can import into Quartus I made to document this.
« Last Edit: May 22, 2020, 06:25:05 am by obiwanjacobi »
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