Jon-

The Silicon Labs chip is not a typical 8051. You are correct about a 
standard 8051, but this chip is more of an 8051 core running at 50 or 100 
MHz. They may have a version with an Ethernet MAC and DMA as well.

Which ARM7 are you looking at? Atmel has some good ones, and I know some 
people who are using Freescale for embedded ethernet products. There are a 
lot of good ARM7 processors out there.

Javid

----- Original Message ----- 
From: "Jon Elson" <[EMAIL PROTECTED]>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Sent: Saturday, October 27, 2007 5:15 PM
Subject: Re: [Emc-users] Ethernet I/O


> 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.
>
> Jon
>
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