| ??? 12/23/10 18:12 Read: times |
#180254 - cross purposes Responding to: ???'s previous message |
Jason Arkwright said:
I've already explained that the '51 requires special design proceedures to overclock given it clocks at either 12 or 6 division xtal clocks, so 30MHz equates to 5 mips, crystals above 30MHz are usually 3rd harmonic which don't oscillate nicely, so a drop in crystal above 30MHz is hard to come by, this is not the case with the AVR. I've already explained that the alternative '51 from Dallas single clocker has only 1kbyte of ram, when the criteria for DSP platform is lots of ram and lots of speed.
Sililabs produce nice chips but they are both expensive and difficult to prototype owing to their smd only package. The other point I wish to stress, is that output port pins on the '51 are normally common source with pull ups on their respective , they reach their limits very sharpish at 5 mips, i.e., looking at the waveforms communicating with a serial 13 bit a/d dont look good, much healthier waveforms can be seen from the AVR, doing the same job, which use the standard DDR in/out format. As the others have said, you are not going to get a modern speedy part in a DIP40 package. However, with a decent soldering iron, some 0.025" solder, solder wick, and a magnifying lens, you should be able to solder a QFP onto a board no sweat. Really. As for the speed thing in general, the SiLabs C8051F120 can run at 100 MHz and it has a MAC with 16x16 multiplier and 40-bit adder that can do the math in two clock cycles (50 Mips). And it has a 12-bit 100 kS/s ADC. Some of their parts in the F360 series have the MAC, too. I think if you want to do DSP, you should maybe consider using a specialist part such as an Analog Devices SHARC or BlackFin or a TI TMS320 device. Most of those devices run rings around microcontrollers (clock speeds up to a Gigahertz). Of course, absolutely none of them come in through-hole packages (see the trend?) and the tools are frighteningly expensive. -a |
