LPC2294 Etherner Extension

Development Boards MicroMod
1

Dears,

I am a student and i need to know how to extend LPC2294 board to support multiple ethernet ports.

Thanks in advance

BISO

2

  • If you want to have good 10/100 alternative of CS8900A, I recommend Micrel KSZ8841. I think DM9000 is poor choice, and LAN9118/9218 is more expensive than KSZ8841.

  • besides proper wiring, it’d be key to have “right values” in BCFG[0-3] registers. HW technician should have the right answer there.

3

  • I should have mentioned to PINSEL2 register for external chip control selection which plays a substantial role.

  • I obtained “LPC2119/2129/2194/2292/2294 USER MANUAL” in PDF form. Dated May 03, 2004, pp.59-60 shows how to hook 32/16/8bit devices with LPC. PLS look at figure 7,8,9 carefully. They explains how D (data), A (address) and BLS (byte lane selector, sometimes called as HBE0…3 or BE0…3) lines communicate LPC with external chips. Note; attention is necessary around A1/A0 lines.

  • Let’s say you choose KSZ8841M-32 for plain 32bit data path and two chips are wired with CS2 and CS3. It should be trivial to hook D0…31 and BLS0…3 lines. Address lines are a bit compilcated. All of BLS0…3 is fed to KSZ8841. The product’s PDF tells A1 line can be GND and A2…15 lines to tie with LPC. LPC offers 24bit (upto A23 line, 16MB) address space for external devices while KSZ is capable of spanning 64KB range. I guess it should be OK to tie only A3…2 in practice since KSZ decoding is so small to distinguish only 8 half (16bit) width register locations.

  • Not forget PINSEL2 to reflect pin assignment reality.

Hope this helps your understanding.

4

Thanks boolthowto alot for your response.

I am still working your suggestion however, is there an easy way to use 3-5 RJ45 Ethernet connectors with LPC2294.

Thanks again

BISO

5

  • LPC has 4 chip select CS0…3 lines and it’d be difficult to have many external chips beyond 4 in principle. It’d be technically possible to hand-craft external gate logic circuit (LS-blahblah) to multiplex/share the lines and address space, however, it’d be rather hard to accomplish. Software burden for the peculiar design will be also a large minus. In general if you tempt to have many chips of the same kind at once, it’s necessary to go smarter than ususal design.

  • but there is a hope. It depends on what you really want. Your needs is to have multiple RJ45 ports to communicate each other and not multiple Ethernet MACs (== Ethernet chip) to behave independently? If so, it’d be a solution to use “Ethernet switch chip.”

http://www.mesanet.com/serialcardinfo.html

The page contains a product named “4I66 MAC-HUB”. The 4 Ethernet ports are self-standing switch indeed. Then powered, traffic goes through them like as a standard Ethernet learning bridge. The switch chip has the 5th port which is tied with a single 10/100 Ethernet MAC, National DP, somehow legacy EMAC. In the end the product offers 4 ports by utilizing only single EMAC to hook.

  • Now let’s see deep in its design.

http://www.micrel.com/_PDF/Ethernet/ks8995xa_pb.pdf

Page 3 figure 2 explains how the Ethernet switch can offer 4+1 configuration. Got it? Note that figure 1 tells how commodity residential SOHO gateway products seen in market shelves are designed under hood. You can choose 8 port model alternatively.

  • Another possiblity would be to use 2 port switch with builtin EMAC, named KSZ8842. This humble product is interesting because the original intent is to act as “T-connector” for Ethernet cabling. We all know that common telephone/FAX units have dual RJ-11 ports at back; one for wall jack (line) and another for “down-stream” unit. KSZ8842 is designed for such the replacement, promising VoIP products to bloom.

  • A pair of KSZ8842 can offer 4 ports, segmented 2 and 2, consuming only two CS lines of LPC. Cross traffic between two KSZ must be managed by software in this case; implementation is a choice from “router” or “software bridge”.

Hope this helps your endeavour.

6

Thanks alot sir you were more than helpful :smiley:

BISO