Wiznet W5300 data stuck in TX buffer

Question

Hello! I’m using Wiznet W5300 with Spartan-6 in 16bit mode for sending data to PC through TCP/IP. Spartan is clocked by 25 MHz, Wiznet TX buffer size is 32 KB. I implement sending process in accordance with algorithm in W5300 DS. But I faced strange thing. When I decrease time of write operation to Wiznet registers to less than 7 clock tacts (~280 ns), some of sended data are stuck in TX buffer. For example I send 1 MB, but PC gets only 980 KB. After increasing write time to 8-9 clock tacts data are sended correctly. Did anyone faced with problem like this?

Eugeny · Answer

Wireshark output of the session would help to see what is going on the network - in both cases.

Aleksandr N · Answer

Thanks for quick response! Here the WS output sessions. I checked both cases again, fixed some errors and find out, that data get stuck in TX buffer when WR time is less than 4 FPGA tacts (160 ns). I send 32 bit counter data to PC. Device IP is 192.168.0.2, port is 5000, packet size is 512 bytes. If WR time is less than 4 tact, almost all data are sended correctly except last 12-13 KBytes. When WR time increases to 4 tact, all data are sended correctly. PS: Files with “.pcapng” aren’t allowed to upload, so I add “.pdf” after their name. wr_time_120_ns.pcapng.pdf (1,5 МБ) wr_time_160_ns.pcapng.pdf (1,5 МБ)

Aleksandr N · Answer

Sorry for slow response, I managed to go back to that job only now. Here’s the screenshot of my read and write cycles in scope. Yes, files have same content before interruption. I tried, it didn’t help. Diagram1505×252 93.3 KB