Wiz812mj spi interface is erratic

Question

4608×3456 433 KB 4608×3456 446 KB Hello, I have added your WIZ812MJ Ethernet module to my existing PIC24HJ based design, to create a TCP Ethernet facility. I gave encountered a problem with reading certain registers. One example is in the attached photos. I am writing 0xAA to address 0x0420 (IMG_0009) and when I read back from 0x0420 I get x08 (IMG_0010). I can do a successful write/read cycle to many registers, but not all. This is causing me a major problem e.g. I cannot read S0_TX_WR for buffer control. Please help, I cannot see what I am doing wrong. Best Regards Mike.

wiznetmuseum · Answer

hey, Wiggum23. i can know your problem. WIZ812MJ Used WIZnet’s W5100 chip. on the datasheet of W5100, address 0420-0421 can’t write. the register must use reading. you says “I can do a successful write/read cycle to many registers, but not all.”, i think it is you can’t check W5100’s datasheet or register’s character. i hope this reply is helpful to you. 868×485 122 KB

WIGGUM23 · Answer

Many thanks for your replies, I made a simple mistake. I still couldn’t write/read to 0x0424 ( S0_TX_WR ) then I found this on another forum :- “Looks like the Sn_TX_WR only gets updated AFTER a successful SEND! You’ll have to keep track of all the writes to the TX buffer and write the TOTAL bytes to send in the Sn_TX_WR register, perform the Send and then Sn_TX_WR can be read and will have the updated value in it.” I am now getting good results but I think this should be added to the datasheet as soon as possible. Best Regards Mike.