Ethernet TJA1101 using S32R274 for REF_CLK

[WenChao]

Hi,

When we were using the TJA1101,we've noticed that there were three options for its clock,and we choose the mode b,using external reference clock.(TJA1101 datasheet page 10,Fig 5.b).

then we linked pin25 of TJA1101 with pinU11 of S32R274 together,and make the pin u11 as output of ENET RMII reference clock,which is 50M.

After this,we could R/W the registers of TJA1101,but we can't PING it.

With a trying of bring another 50M directly into the pin25 of TJA1101 from outside,we can finally PING it sucessfully.

My question is,if using pinU11 of S32R274 as an output of 50M for pin25 of TJA1101 as the reference clock is right?

IF it's right,why can't we PING it;IF it's wrong,please tell me why.

FYI,the wire bitween the pinU11 of S32R274 and the pin25 of TJA1101 is about 1050mil in our PCB.

looking forward to your reply.

best regards.

WEN.

[Bulat]

It does not matter for the TJA1101 what is the source of 50MHz clock, S32R is also ok. Try to check with a scope if the S32R really generates the clock signal at U11 pin. Probably frequency is not 50MHz or there are problems with its shape/quality.

Regards,

Bulat

[WenChao]

Hi,Bulat

Thanks for your reply.

Maybe there's a misunderstanding between us.

Our design is based on the project Cocoon2_ATB-NXP from the RFbean as attached.We've connected the pin25 of TJA1101 with the pinU11 of S32R274 together,only these two pins.And then we configured the pinU11 of S32R274 as an output of RMII reference clock(50M),But we can't make the PING.

So we changed the pinU11 of S32R274 to input as RMII reference clock(50M),and linked them with another 50M clock from outside,then the PING is ok.

So, my really question is,if we can linked the two pins together without any other clock?if it's possible,how to configure the pinU11 of the S32R274.

FYI,I've compared the clock from the pinU11 with the outside one,i didn't see anything special,cause the outside one is also come from the pinU11 of S32R274 on the other board. 

Thanks again,and looking forward to your reply.

BR,

WEN

[Bulat]

First I thought you suspected the problem is with TJA1101. However it looks like the problem is rather with S32R configuration. You wrote "So we changed the pinU11 of S32R274 to input as RMII...", what are the exact changes you did when changed "pinU11 of S32R274 to input as RMII"?

Regards,

Bulat

[WenChao]

Hi，bulat

the pinU11 of S32R274 has several kinds of configurations.

 we are using the RMII mode of TJA1101,so we connected the pin25 of TJA1101 with the pinU11 of S32R274 together directly,and configured the pinU11 of S32R274 as an output,but it can't work. 

 when we changed it into input,and bring another clock within these two pins,we can make the PING.

[Bulat]

Ok, with original configuration (REF_CLK is output at S32R side), can you try to set IBE bit of MSCR107 register?

[WenChao]

Hi,bulat

Sorry for taking so long to reply you,my friend.

Anyway,I've tried to set IBE bit of MSCR107 register from 0 to 1,but i didn't get the result i wanted,the PING still can't be made.

because of the deadline,I am using the other way to given the clock.

If you have some other ideas,please tell me,I'm still interested in this question.

BR.

Wen