WIZ812MJ and other SPI Devices - Question

Forum 2005-2010 (read only) Hardware Troubleshooting
#1

Hi

I have read on here that there have been issues with some Wiz Ethernet devices not releasing the SPI bus correctly when they are no longer selected by the chip select. I am just wondering if the WIZ812MJ is one of these devices, or if it does behave correctly?

I am just desigining a circuit to plug the WIZ812MJ into, and so would like to know if I have to add a transistor or anything to a pin to enable this to work correctly.

I have seen the Freetronics ethernet shield which corrects this problem, however it looks like they switch the SEN pin which doesnt appear to be broken out on the WIZ812MJ's pins. Is the issue fixed already or do I need to do something?

Can anyone assist please?

Thanks James

#2

Just found this in the 1.1 datasheet which I didnt spot before:

/SCS (Slave Select) * This pin is used to SPI Slave Select signal Pin. This pin controls SPI_EN signal of W5100. When /SCS signal assert low, W5100 drive SPI mode by SPI_EN signal toggled high.

SPI_EN is the SEN pin, so I am assuming this issue isnt a problem with the WIZ812MJ and other slave SPI devices on the same bus?

Cheers

#3

Bah im stupid. The datasheet I got didnt download all the pages so didnt get the schematic at the end.

/SCS goes into a dual schmitt inverter by the looks of it, and SPI_EN (SEN) comes out, so that is what I was after.

All is good.

#4