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'[EE] Need 5V CPLD'
2011\03\04@143619 by Dwayne Reid

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Good day to all.

I'm tackling another project where I need to intercept a SPI data stream and modify the data on the fly.  I'm only interested in modifying the data feeding a pair of 74hc595 shift registers but the SPI buss is used for talking to lots of different devices.  There is a separate Latch line that latches the data into the two shift registers at the appropriate time.

So: I have to continually buffer two bytes worth of data until the Latch line becomes asserted.  I'll then modify the data and spit it out to the shift registers.

I haven't even put a scope on this beast yet to see how fast the SPI data is but I suspect that its pretty quick - there are a lot of devices on the buss that are updated in real time.

Although my first thought was to use a PIC that can do hardware SPI slave, I'm not sure if its fast enough.  I'll find out later today when I put a scope on the SPI buss.

Assuming that the PIC isn't fast enough, my next thought was to use a small CPLD.  Therein lies my problem.

All of my CPLD experience is with old Intel / Altera parts: ep320, ep610, ep910, epm7032, epm7128.  The last of those projects was around 15 years ago and written in Altera's Advance Design File or Text Design File formats (.ADF, .TDF).  I have no experience with Verilog or VHDL.

That's the software side.  The hardware side is also a little challenging: the SPI buss and those shift registers are running from 5Vdc.  Most modern CPLD's seem to be 3.3V or lower.

So: I'm looking for suggestions for a small to medium size CPLD that runs at 5V and has at least 40 macrocells.  I can probably get away with fewer macrocells (as few as 24) if I generate the output data on the fly (rather than loading a 16-stage shift register and shifting the data out) but I'd have to see how flexible the product term array is for that kind of thing.

I'd appreciate any suggestions or opinions that others might have.

Many thanks!

dwayne

-- Dwayne Reid   <spam_OUTdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2011\03\04@150022 by Philip Pemberton

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On 04/03/11 19:36, Dwayne Reid wrote:
> That's the software side.  The hardware side is also a little
> challenging: the SPI buss and those shift registers are running from
> 5Vdc.  Most modern CPLD's seem to be 3.3V or lower.
>
> So: I'm looking for suggestions for a small to medium size CPLD that
> runs at 5V and has at least 40 macrocells.

The Xilinx XC9500 series was still in production last time I checked, but very expensive.

You'd be better off getting a couple of 74LVC or 74LVX chips to use as bus translators, and use an XC9500XL series chip (3.3V). Far cheaper, and far easier to obtain parts...

Heck, the I/O pads are 5V tolerant -- if your hardware doesn't mind being driven from 0V/3.3V TTL, you can do away with the buffers and wire the CPLD straight in.

Only thing you'd need to add is a low-current 3.3V power supply. An LDO would be the ideal, something like an LP5951MF-3.3 (NatSemi) or ZXCL330 (Zetex / Diodes Inc). One chip (30p ish) and two cheap ceramic capacitors is all you need.

-- Phil.
.....piclistKILLspamspam@spam@philpem.me.uk
http://www.philpem.me.uk

2011\03\04@150304 by Isaac Marino Bavaresco

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Em 4/3/2011 16:36, Dwayne Reid escreveu:
{Quote hidden}

Altera's MAX7000S series supports 5V I/Os, MAX3000 series have 5V
tolerant I/Os.


Best regards,

Isaac

2011\03\04@164819 by Dwayne Reid

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At 01:00 PM 3/4/2011, Philip Pemberton wrote:
>On 04/03/11 19:36, Dwayne Reid wrote:
> > That's the software side.  The hardware side is also a little
> > challenging: the SPI buss and those shift registers are running from
> > 5Vdc.  Most modern CPLD's seem to be 3.3V or lower.
> >
> > So: I'm looking for suggestions for a small to medium size CPLD that
> > runs at 5V and has at least 40 macrocells.
>
>Heck, the I/O pads are 5V tolerant -- if your hardware doesn't mind
>being driven from 0V/3.3V TTL, you can do away with the buffers and wire
>the CPLD straight in.

I considered that but the existing shift registers are HC rather HCT.


>Only thing you'd need to add is a low-current 3.3V power supply.

This unit actually has 3.3V, 1.8V, 1.25V rails for the TMS320xx DSPs and all of the codecs.  But these shift registers are being used to control analog gate packages that want to see a 5V control signal.

Thanks for the suggestions!

dwayne


-- Dwayne Reid   <dwaynerspamKILLspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2011\03\04@170258 by Dwayne Reid

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At 01:03 PM 3/4/2011, Isaac Marino Bavaresco wrote:

>Altera's MAX7000S series supports 5V I/Os, MAX3000 series have 5V
>tolerant I/Os.

Thanks for the suggestions.

I've used the MAX7000 series devices previously - epm7032slc44 and epm7128slc84.  I had assumed that they were obsolete.  I've only got something like 15 pcs of the 7032 still in stock.

Come to think of it, I think that I still have a few hundred ep600 or ep610 devices hanging around.  But they are only 16 macrocells - at least 8 too few and way too much hassle to split among multiple packages.

I just checked <http://www.findchips.com> and they show that Digikey lists the 7032 but with zero stock.  Quest has them for $7 in the quantities that I need.

I'm still looking for other options but this is going to be my fallback plan.

Thanks again!

dwayne

-- Dwayne Reid   <.....dwaynerKILLspamspam.....planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2011\03\04@182408 by Mike Harrison

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On Fri, 04 Mar 2011 12:36:06 -0700, you wrote:

{Quote hidden}

Couple of suggestions -
SPI isn't exactly a lot of lines so may be cheaper to level-convert to 3.3 & back & use a cheap
modern CPLD
I think Atmel's ATF PLDs are still available - these were programmed in CUPL (Free from Atmel) which
may be more familiar with what you were using in teh past. Many of the NXP ARMs have two SPI ports, which may be fast enough. You may even to be able to do bit
manipulation on the fly bit-by-bit.

2011\03\04@185220 by Philip Pemberton

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On 04/03/11 21:48, Dwayne Reid wrote:
> This unit actually has 3.3V, 1.8V, 1.25V rails for the TMS320xx DSPs
> and all of the codecs.  But these shift registers are being used to
> control analog gate packages that want to see a 5V control signal.

Quick back of the envelope calculation based on current Farnell prices...

Xilinx XC9572-15PCG44C   -- £5.40 each 1-off, £3.90 each 10-off.
Xilinx XC9572XL-10PCG44C -- £2.11 each 1-off, £1.86 each 10-off.
STMicroelectronics 74LVX04MTR -- 18p each 1-off, 12.2p each 10-off.

So we have two solutions. Let's say we're making ten of these things:
  XC9572 alone         -- £3.90 each
  XC9572XL and 74LVX04 -- £1.97 each

Take 5V from your main power rail, run the LVX04 from that. Run 3V3 from your DSP supply and run the 9572XL from that. Inputs to the 9572XL go through 33-ohm current limiting resistors, outputs go through the LVX04 (which boosts the voltage to 5V).

The 3V3 solution reduces cost by almost half, and stock availability is MUCH better. It uses more board area, but if you're installing a bodge-board that probably isn't a major issue (it's maybe an extra square inch for the LVX04).

-- Phil.
piclistspamspam_OUTphilpem.me.uk
http://www.philpem.me.uk/

2011\03\04@224709 by cdb

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::t ake 5V from your main power rail, run the LVX04 from that. Run 3V3
:: from your DSP supply and run the 9572XL from that. Inputs to the 9572XL
:: go through 33-ohm current limiting resistors, outputs go through the
:: LVX04 (which boosts the voltage to 5V).

Doesn't the 74LVX04 go the wrong way for this scenario? Isn't it a 5v5 in and 3v3 out type device?

According to the Fairchild datasheet, VO = Vcc and max Vcc is 3v6.

Were you thinking of the 74LVC4245A which can take 3v3 and boost it to 5v5? I'm thinking of using one of these to interface a Pic24 to a 5v GLCD.

Colin --
cdb, @spam@colinKILLspamspambtech-online.co.uk on 5/03/2011
Web presence: http://www.btech-online.co.uk   Hosted by:  http://www.justhost.com.au
 

2011\03\05@002503 by Andre Abelian

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Dwayne,

Speaking of CPLD programming you can first draw logic schematic then in simulate it see
if it works then in xilinx or altera IDE you can put together same schematic and you are done it will generate code for you. you can also do opposite write code and it will generate logic schematic.

Verilog is very similar to C

Andre




________________________________
From: Dwayne Reid <KILLspamdwaynerKILLspamspamplanet.eon.net>
To: pic microcontroller discussion list <RemoveMEpiclistTakeThisOuTspammit.edu>
Sent: Fri, March 4, 2011 11:36:06 AM
Subject: [EE] Need 5V CPLD

Good day to all.

I'm tackling another project where I need to intercept a SPI data stream and modify the data on the fly.  I'm only interested in modifying the data feeding a pair of 74hc595 shift registers but the SPI buss is used for talking to lots of different devices.  There is a separate Latch line that latches the data into the two shift registers at the appropriate time.

So: I have to continually buffer two bytes worth of data until the Latch line becomes asserted.  I'll then modify the data and spit it out to the shift registers.

I haven't even put a scope on this beast yet to see how fast the SPI data is but I suspect that its pretty quick - there are a lot of devices on the buss that are updated in real time.

Although my first thought was to use a PIC that can do hardware SPI slave, I'm not sure if its fast enough.  I'll find out later today when I put a scope on the SPI buss.

Assuming that the PIC isn't fast enough, my next thought was to use a small CPLD.  Therein lies my problem.

All of my CPLD experience is with old Intel / Altera parts: ep320, ep610, ep910, epm7032, epm7128.  The last of those projects was around 15 years ago and written in Altera's Advance Design File or Text Design File formats (.ADF, .TDF).  I have no experience with Verilog or VHDL.

That's the software side.  The hardware side is also a little challenging: the SPI buss and those shift registers are running from 5Vdc.  Most modern CPLD's seem to be 3.3V or lower.

So: I'm looking for suggestions for a small to medium size CPLD that runs at 5V and has at least 40 macrocells.  I can probably get away with fewer macrocells (as few as 24) if I generate the output data on the fly (rather than loading a 16-stage shift register and shifting the data out) but I'd have to see how flexible the product term array is for that kind of thing.

I'd appreciate any suggestions or opinions that others might have.

Many thanks!

dwayne

-- Dwayne Reid   <spamBeGonedwaynerspamBeGonespamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2011\03\05@052757 by Philip Pemberton

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On 05/03/11 03:47, cdb wrote:
> Doesn't the 74LVX04 go the wrong way for this scenario? Isn't it a 5v5 in
> and 3v3 out type device?
>
> According to the Fairchild datasheet, VO = Vcc and max Vcc is 3v6.
>
> Were you thinking of the 74LVC4245A which can take 3v3 and boost it to 5v5?
> I'm thinking of using one of these to interface a Pic24 to a 5v GLCD.

I'm glad someone's paying attention!

LVX, LVC, one letter difference and a load of trouble if you mix them up!

I actually meant the 74LVC04, but the 74LVC4245 is an even better choice. "I plead a momentary lapse in judgement your honour!"

-- Phil.
TakeThisOuTpiclistEraseMEspamspam_OUTphilpem.me.uk
http://www.philpem.me.uk

2011\03\05@054910 by Mike Harrison

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On Sat, 05 Mar 2011 10:27:53 +0000, you wrote:

>On 05/03/11 03:47, cdb wrote:
>> Doesn't the 74LVX04 go the wrong way for this scenario? Isn't it a 5v5 in
>> and 3v3 out type device?
>>
>> According to the Fairchild datasheet, VO = Vcc and max Vcc is 3v6.
>>
>> Were you thinking of the 74LVC4245A which can take 3v3 and boost it to 5v5?
>> I'm thinking of using one of these to interface a Pic24 to a 5v GLCD.

I normally use bog-standard  74HCT for 3.3->5V - very cheap and available.

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