Xilinx XAPP169 Manuel d'utilisateur télécharger pdf (Page 25)

MP3 NG: A Next Generation Consumer Platform

XAPP169 (v1.0) November 24, 1999 www.xilinx.com 25

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Spartan Device

Selection

Spartan devices are available in a range of densities and packages. The following criteria were

used to select the device used in this application:

• I/O Pins. The design requires a total of 137 I/O pins. I/O pin requirements per block are

summarized in FPGA Resource Usage Summary.

• Voltage. The design operates at 3.3V.

• Density. The estimated

size of the design is 83,000 gates, with the usage broken out in

Tabl e 8.

• Performance. The highest clock speed used in the device is 64 MHz, used to clock the

SDRAM controller state machines. The remaining logic runs at sub multiples of this clock

rate.

• Packaging. The size constraints imposed on most modem designs dictates a high-density

surface mount package.

Based on these criteria the device selected for this design is the XC2S100. This device offers

100K gates density, 3.3V operation, 176 user I/O, and is packaged in a space saving FG256

BGA package.

Conclusion The design that has been outlined meets both original design objectives. Even with budgetary

pricing the cost of the solution is well below $100. Table 9 shows the cost breakdown of the

system. The design also has enough spare resources both in terms of CPU cycles and FPGA

gates to support field upgrades. Operating at a core clock speed of 64 MHz, the RC32364 will

provide enough performance for both audio decoding and user interface functions. By locking

the audio decode functions in the instruction cache a significant increase in system

performance as well as reduced power consumption is achieved.

This design also illustrates how manufacturers can create designs that the optimized

integration of an ASIC while supporting the manufacturing and field upgrade flexibility of an

FPGA.

Table 8: FPGA Resource Usage Summary

Interface CLB Usage Number of Signals

CPU 25 51

LCD Display 58 9

IRDA 59 3

USB 21 3

DAC 23 5

ADC 0 3

SDRAM 100 9

FLASH 100 10

CompactFlash 100 17

Memory Address Bus 4 11

Memory Data Bus 10 16

Total: 500 137

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