Floating-point DSP gets “RISCy”
By Robert Cravotta -- EDN, April 15, 2004
Processors that integrate a DSP core with a microcontroller core on one device are becoming increasingly common. Atmel’s Diopsis AT572D740 continues this trend by integrating a VLIW (very-long-instruction-word) mAgic DSP core with an ARM7TDMI microcontroller core. However, this integration differs from the other DSP/RISC integration offerings because the mAgic core is a single-cycle, complex, floating-point DSP. It is becoming more feasible to consider using a floating-point DSP instead of porting floating-point algorithms to a traditional fixed-point core as process geometries continue to shrink; on-chip memory is becoming the significant user of real estate, and the cost of implementing a floating-point architecture is shrinking relative to the system cost. The Diopsis processor, operating at 100 MHz, typically consumes 0.8W and 1.4W in the worst case (Picture).
The mAgic core’s native support for complex floating-point operations makes it a candidate for frequency-domain algorithms, time- and frequency-domain analysis, and frequency-spatial wave-number algorithms that would benefit from or require the extra range and precision of 40-bit floating-point data. The mAgic core targets heavy floating-point algorithms and can perform 10 floating-point and pipelined-complex-arithmetic operations per cycle. The AT572D740 includes two SPI serial ports, two USARTs, a timer/counter, watchdog timer, a parallel-I/O port, a peripheral-data controller, eight ADC and eight DAC interfaces, a clock generator, and an interrupt controller.
The control registers and memories of the mAgic DSP map directly into the ARM memory space so that the ARM can read or write the DSP local data memories and configuration registers. In system mode, the ARM can modify the DSP program memory by initiating a DMA transfer from the external memory or by directly writing four 32-bit words to four consecutive addresses at the appropriate program-memory location. In run mode, the ARM may access only the mAgic command register and a 1000×40-bit, dual-port shared memory Both processors operate their own programs, and either processor may operate as the master.
The MADE (Modular Architecture Developing Environment) supports DSP and RISC code development in one environment. That support includes C compilers for the ARM and mAgic cores, a macro assembler/optimizer, visual debuggers and simulators, and Light RTOS. The Diopsis AT572D740 is available now in a 352-ball PBGA industrial-temperature-range package for $30 (1000).
Atmel, 1-408-441-0311, www.atmel.com.
