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Interfacing Pmod NIC100 with EMSK


Dhanuraj Pillai

Question

Hello,

I would like to use the Digilent Pmod NIC100 Rev B with EMSK from Synopsys (I dont have it yet)to get Ethernet 100Mbps communication via SPI.

So some silly questions as I am have not used Pmods till now :)

So if my understanding is correct, the Pmod device should be configured as an SPI Slave to my EM SK and the Pmod shall unpacket the SPI Stream and use its preprogrammed MAC inside Microchip ENC424J600.

But now it needs a TCP/UDP stack over it . The below statement in the explanation confuses me:

"Users must provide their own protocol stack software (such as TCP/IP). Digilent provides a set of libraries providing Ethernet support that is available in the Pmod NIC100 Resource Center. "

I checked the schematics of the Pmod , I did not find a JTAG/BDM interface.

My question is:

1) The Pmod NIC100 has a Microchip, and program it via any extra in programming interface or how is it done ?

2) The SPI inteface according to Microchip is of max 16M and obviously it is SPI. So how is 100 Mbps on Ethernet achieved , won't there be a bottleneck ? Or some extreme buffering of frames are happening inside the Pmod?

Answers to these questions would help me greatly to decide to order these boards or not. :)

Thanks in advance for your answers.

Best Regards

Dhanuraj

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2 answers to this question

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I would certainly encourage you to start with the datasheets and MicroChip documentation to see what you are getting into before making a selection.

The SPI interface is indeed the limiting factor in data throughput. But the devices have other interface modes... if the board design takes advantage of it. You can find the information that you need at MicroChip. There's no software programmable capability in these devices.

If you need basic Ethernet connectivity and can write a driver these might be something to consider, as long as you understand what you are getting into and don't care about throughput or latency.

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Hi Zygot, thanks for your answer.

So for the moment I can leave aside the bottleneck of SPI interface coming in between to Ethernet .

Good that you can confirm that it has no programming/reprogramming capability. This was also my understanding when I went through the manual and schematics.

My aim is to use the EMSK (EM Starter Kit) for our programming platform making use of its ARC EM4 cores. Given the deadlines, this itself is a huge project for me.

 EMSK has no Ethernet hardware interface, thats why I'm trying to get Pmod as a piggyback to get an Ethernet hardware interface, so that a stack implementation(UDP, TCP ) can be written/ported and tested on ARC EM4. instead of Ethernet driver an SPI driver shall do the job of communicating with Pmod Microchip and con

So when Digilent writes :"Users must provide their own protocol stack software (such as TCP/IP). Digilent provides a set of libraries providing Ethernet support that is available in the Pmod NIC100 Resource Center. "
This statement is not so clear to me. Do they mean this 'protocol stack software' in my case goes into my EM4 (Master) or in Microchip NIC100 (Slave)?

I would appreciate any kind of tips or also if some one has used this Pmod like this 

Thanks

Dhanuraj

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