Brian Michalk wrote: > I've done a bit of programming and circuit board design with Silicon > Laboratories 8051 chips. They have an ethernet developers kit complete > with schematics. > http://www.silabs.com/tgwWebApp/public/web_content/products/Microcontrollers/en/EthernetDK.htm > > > > I have not priced the components, but a board should cost less than $20 > each. The 8051 is not a good choice for real time control of motors at high precision. I suspect that an 8051-based interface might just barely be able to keep up with a 1 KHz servo update rate (2000 packets/second received, 1000 packets/sec sent back to PC). I'm hoping to be able to turn up the servo update rate quite a bit with this system. The chip that I've been looking at has a 10/100 Mbit/sec ethernet MAC on chip, with DMA transfer to dedicated on-chip RAM. It is based on the 32-bit ARM7 processor, which is likely to be hundreds of times faster at handling the ethernet protocol. Even at 1 KHz servo rate, it would have to receive a request from the PC, decode it, perform the requested register reading and then build a packet to send back to the PC. The PC would take 50 us or so as do the PID calculations and then send a velocity command packet to the device. It would be good to handle each request in maybe 100 us or so. I have great doubts that an 8051 could process the protocol stack and do the I/O in 25 or so instructions.
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