[SOLVED] Problem with ARM microcontroller ethernet controller and DP23848 chip

[amirahmadian]

Problem with ARM microcontroller ethernet controller and DP83848 chip

Hi,
I've written a simple program for LPC1768 microcontroller (ARM Cortex-M3) in order to interface ethernet network, I just need to receive network packets at the first step. I've used DP83848C chip as the PHY (via RMII interface). For the 10Mb/s ethernet everything works well and I'm able to receive packets (frames) corrrectly (I have tested it with JTAG Debug). But the problem is for 100Mb/s mode. When the network works at 100M speed, the packets are received incomplete (truncated) and some bytes in the end of the packets are not received. Even sometimes the entire packet is missed! Since my program works very well in 10Mb mode, I doubt if there is a problem in software or hardware.
Other information:
1. I set the PHY at Auto Negotiation mode
2. I set the IPGT and SUPP registers correctly according to duplex and speed mode
3. I use IAR compiler

 

[amirahmadian]

Fortunately I fixed the problem myself! The problem arised from CPU clock. I hadn't configured PLL correctly. So remember you MUST always configure the clock prior to using the ethernet unit.

 

[bigdogguru]

Re: Problem with ARM microcontroller ethernet controller and DP83848 chip

Since my program works very well in 10Mb mode, I doubt if there is a problem in software or hardware.

Of course the real lesson is not falling into this mindset.

If the problem exists in neither the software nor hardware, where could it exist?

BigDog