I’m working on a project based on a LPC2388 and a Micrel KSZ8721 chip. I purchased a kit from Olimex (LPC2378 board) and I found out there was a mistake on the schematic : the pin 22 (CRS) and the pin 9 (CRSDV) of the Micrel are connected together on the board (a small wire below the chip has been added) but it is not mentionned on the schematic :?:
Why these pins are connected together ? I don’t know if it same on the others designs from Olimex (LPC2468/78 for instance) but on the Keil board (LPC23xx), the chip used is a Micrel too (almost the same chip) and both signals are separated…
It seems Mark from uTasker (wonderfull project BTW) has no explanation regarding this issue.
I read the Micrel datasheet, the pin 22 (E_CRS) should not be used in RMII mode. Only the pin 9 (E_CRSDV) should be connected straightway to the MAC (E_CRS input).
My design is based on Olimex schematic and I’ve found out this issue during the developpment of my prototype. I’ve connected both pin 22 and pin 9 together like Olimex and my emac driver has worked. 100 boards are produced and all worked fine. If I disconnect them (pin 22 floating and using CRS_DV pin 9 only), I received nothing…
On the next production, none worked fine except one… nothing has changed on the PCB side for Ethernet (same LPC revB, same Micrel, same connector, same PCB). My emac driver seems to work : Phy address is detected (0x01), auto-negociation is activated and find the right network features (tested with 10/100M, Half/full duplex too). I set up the MAC module according to the PHY. The oscillator is ok otherwise I could not communicate with the PHY at all. There is problem when I receive packet, the MAC returns an error (CRC error, packet length error… I don’t know exactly since it is OR logic).
As I don’t know why these 2 pins must be connected together, I wondered if there is something to do in the PHY chip… Any tip ? idea ?
david_f:
As I don’t know why these 2 pins must be connected together, I wondered if there is something to do in the PHY chip… Any tip ? idea ?
I have no idea either. If I were you I'd contact 'hasiptuna' who started that discussion.
hasiptuna:
I found problem.Problem is at Olimex kit schematic. 22 number pin of KS8721 is wrong connection. This pin is E_CRS.This pin have to connect 9 number of KS8721.
I have (finally) checked my board using a magnifying glass but can’t see any extra wires connected.
Whether people show their email addresses in the uTasker forum depends on their preferences, but you can always send a personal email via the forum (see “Send this member a personal message.” when viewing the member’s details).
I have however send a mail to “hasiptuna” with link to this thread in the hope that he may be able to put us all out of our misery by filling in on the missing information.