how to evaluate the needed number of gate?

hello all,

For a hobbyist purpose, I want to drive an LCD display (320x240) with a CPLD or FPGA in a standalone device (weather station). I've already played with FPGA and VHDL for some projects but I was never involved in the hardware part of such projects.

The CPLD would have to read data (bitmap picture) from a dual port RAM and write it to the 4 bit data input of the LCD controller (+control lines, clock...). On the other side of the RAM, a microcontroller will update sometimes the content of the picture to be displayed.

I would like to know how to estimate the number of gate needed for the project in order to buy the cheapest CPLD that fits the number of gate.

Do I need first to design the VHDL part and synthetize to know the number of gate and then choose the CPLD?

I do not really understand the difference between CPLD and FPGA and what is better for me.

For a CPLD, the configuration is non volatile and in the FPGA it is volatile so a reconfiguration is needed on each start (via configuration EEPROM or JTAG programming) but the FPGA is much more powerfull. Correct?

Is a CPLD enough for my project? I'm turning around Xilinx XC9536 which seems to be very often used nowadays, is it a good choice for this project?

Many thanks by advance.

Reply to
Mouarf
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That is my preference. IMHO, CPLD's can be a real pain if one underestimates the size and or fan-in. Also, the implementation is more sensitive to the pin out selected. As a point of reference (FPGA), a monochrome EL display (160x120) used

486/4992 (9%) LE ACEX1K EP1K100FI256-2 40,960/49152 (83%) memory bits (two frames in DP RAM)

-- not a particularly good LE to DP RAM ratio.

Some CPLD's have really low power. Most FPGA's have on board memory that can be conveniently utilized. A uP with dual port ram, and logic could be packaged in a single FPGA chip to drive the LCD display. I've seen some FPGA evaluation boards that claim to do this. The Xilinx website has some boards and links to other vendors that sell this stuff. You may be able to get some other data points from this in order to estimate the amount of logic needed.

There was some talk about someone having an FPGA with configuration flash on board the FPGA, but I can neither confirm nor deny this assertion. An FPGA can be configured from non-volatile storage via a uP too.

I would estimate the amount of Dual Port RAM bits required to see if I could get rid of the discrete dual port RAM by using resources in the FPGA. If a suitable FPGA can be found with a good DP RAM to LE ratio, I would further research the cost in an attempt to justify using an FPGA, which I think would be more fun :,)

-- Newman

Reply to
newman5382

--

--Ray Andraka, P.E. President, the Andraka Consulting Group, Inc.

401/884-7930 Fax 401/884-7950 email snipped-for-privacy@andraka.com
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"They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, 1759

Reply to
Ray Andraka

Since this a learning experience for you I'd suggest that you design, simulate and synthesize it before you attempt to build any hardware. The best way to get a feel for what a logic family is capable of is to try a number of designs. After a while you'll be able to look at a project and know what the right device is.

Reply to
General Schvantzkoph

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Correct?

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FPGA

I believe Lattice does have non-volatile FPGAs. I suspect they're a bit pricey.

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Best wishes, --Phil Martel

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fun

Reply to
Phil Martel

OK,

I've tried a simple project in Lattice ispLever software and it tells me the number of pin used, number of registers and the number of logic pterms. Are the pterms equivalent to macrocell?

"General Schvantzk>

Reply to
Mouarf

the

no

Reply to
Antti Lukats

and are the macrocells almost equivalent between devices of the same range from different manufacturers?

"Antti Lukats" schrieb im Newsbeitrag news:co7gt3$4gl$04$ snipped-for-privacy@news.t-online.com...

Reply to
Mouarf

An easy answer is that you would like to download software from each of those manufacturers try your design on each of them. I am going to do just that.

vax, 9000

Reply to
vax, 9000

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