was introduced in 2009 and it was a success. Lower cost on development boards, ICs, and free development tools make it a nice add-on for embedded systems that required more computing power (or multiple IO ports - or interfaces) while keeping reasonably cost for such applications. After the Xilinx were introduced a year later the question was not if but when. Spartan-7 was announced in 2015 - with full production available in 2017.
Here are the main differences between both FPGAs:
Spartan-6 XC6SLX4 XC6SLX150 | Spartan-7 XC7S6 XC7S100 | |
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Technology | 45nm | 28nm |
Design Suite | ||
Logic cells (min/max) | 3, 840 / 147,443 | 6000 / 102,400 |
Flip-Flops (min/max) | 4,800 / 184,304 | 7500 / 128,000 |
Total Block RAM (Kbits) (min/max) | 216 / 4,824 | 180 / 4,320 |
DSP Slices (min/max) | 8 / 180 | 10 / 160 |
I/O pins (min/max) | 102 / 576 | 100 / 400 |
A few considerations:
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Xilinx has archived the ISE Design Suite in favor of Vivado. The latest release was while Vivado keeps improving and you can expect two releases per year.
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Xilinx has "two tiers" for it's development tools, Webpack which is free and the paid version(s). As far as could check, Spartan-7 devices are supported on the free .
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The Block RAM in the Spartan-6 is grouped in 18Kb blocks, while the Spartan-7 is in 36Kb blocks.
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Spartan 7 Block RAMs offer faster FIFO implementations, cascading options, and ECC among other features
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The DSP blocks are different. While the Spartan-6 DSP48 is built on an 18x18 signed multiplication logic, the Spartan-7 offers a 25x18 multiplier plus other architecture differences that can increase throughput.
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Spartan-7 devices do not have transceivers like the Spartan-6 LXT FPGAs, but you can go to the Artix-7 FPGAs.
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XADC: the Spartan-7 comes with a 1 MSPS ADC to internally monitor voltage and temperature, plus external inputs that can be used to monitor board signals.
Spartan-7 FPGAs are based on the 7 Series family, with a smaller technology (implying lower cost / lower power) and furthermore leveraging in a series of architectures updates that increase computing power significantly.
Also, check for further and deeper information.