RISC-V Processor Family Spans from Low-End to 64-Bit with FPU

As part of its Cortus IC Design Service offering, Cortus has announced the general availability of a complete range of RISC-V processors. These are now available for design-in in customer ASIC designs implemented by the experienced teams at Cortus. A wide range of application needs are covered by the 6 processor cores.

The range starts with a low gate count, very low power 32 bit CPU core—the APS1V (RV32EMC). A more powerful, but equally low power CPU, the APS3V (RV32IMC) comes next. If a multi-core solution is necessary the APS5V (RV32IMAC) is available. If floating point is needed then the single precision FPS6V (RV32IMACF) can be used or the FPS8V (RV32GC) for double precision calculations. The last member of the family is a high performance 64-bit processor with double precision floating point and MMU: the FPS69V (RV64GC).
These processors have already been implemented in customer projects in the aerospace, satellite, industrial and automotive sectors. A complete development ecosystem is available, including graphical environment, compiler, debugger real time operating systems and tools. Billions of chips containing Cortus IP (including processor IP) have been manufactured based on the successful Cortus Ecosystem.

Cortus | www.cortus.com

Numeric Precision vs. DDS Calculations

Using the full frequency resolution of a direct digital synthesizer chip outstrips the capabilities of floating point numbers. Ed takes a look at what’s needed for high-resolution frequency calibration and measurements.

By Ed Nisley

As you saw in my July article, the filter bandwidths and frequency resolution required to characterize low-frequency quartz resonators far exceeded the capabilities of my bench instruments. I decided to take a look at building a special-purpose resonator tester around a cheap direct digital synthesizer sine-wave source, because DDS generators have

PHOTO 1 A knockoff Arduino Nano controls a generic AD9850 direct digital synthesizer circuit, both plugged into standard 0.1 inch headers, with hand-wiring connections below the proto board. The SMA connector provides a mechanically rugged output from the board; the DDS frequencies don’t require its RF properties.

PHOTO 1
A knockoff Arduino Nano controls a generic AD9850 direct digital synthesizer circuit, both plugged into standard 0.1 inch headers, with hand-wiring connections below the proto board. The SMA connector provides a mechanically rugged output from the board; the DDS frequencies don’t require its RF properties.

advantages over traditional analog oscillators and frequency counters in computer-controlled measurement systems.

Of course, nothing is ever so simple as it seems. In this article, I’ll explain how numeric precision affects Direct Digital Synthesis (DDS) output frequency calculations, work through the effects of floating-point and fixed-point arithmetic, and show how a carefully tweaked DDS oscillator frequency varies with temperature.

DDS Calculations

You can think of a direct digital synthesizer as a lookup table holding the digitized values of an analog waveform, a counter addressing the table entries in ascending order, and a DAC converting the numbers to analog voltages. The Analog Devices AD8950 DDS chip in Photo 1 has the equivalent of a table with 232 10-bit entries defining a sine wave, a counter clocked at 125 MHz, and a differential output current-mode DAC. The PCB, complete with the DDS and a 125 MHz quartz oscillator, costs under $20 on eBay or Amazon. …

Read the full article in the September 326 issue of Circuit Cellar

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