- Overview
S32X-MB is a mother board of S32Z/E and S32K396, which is for extending the peripheral interfaces with multiple PHYs and pins. Users will face problems when using TJA1103 PHY on S32X-MB. This article is to notice the issues to users.
- Two hardware issues of TJA1103 PHY on MB
1. Pin strapping, TJA1103 can’t be configured as master mode when autonomous mode is enabled.
2. TJA1103 data unstable transmission, the clock signal has length 30 cm on the board but in the specification the maximum length of this signal is maximally 15 cm.
- Details of the two issues
1. Pin strapping: According to TJA1103 Datasheet, pin strapping should work as below. Actually, it is not exactly. Exceptions are, when CONFIG5 and CONFIG6 are set as both "H", TJA1103 works in master mode when not connecting slave board while TJA1103 works in slave mode when connecting slave board. If CONFIG5 and CONFIG6 are set both "O", TJA1103 works in slave mode regardless of whether slave board is connected or not.
2. TJA1103 data unstable transmission: There will be packet loss when transmit/receive packets with 100% line rate. There is possibility that packets drop with line rate less than 100%.
- workaround
Current TJA1103 on the S32X-MB is a chip of old version with lower driving capability compared with new one. Pin strapping with “O” required CONFIG5 and CONFIG6 detecting voltage transition in a very short time window. Current TJA1103 on S32X-MB failed to drive signal at required voltage level in such a short time. Mode setting failure can be solved by
1. Replacing TJA1103 from S138X to S4070 version
2. Resetting PHY after power on
Both steps need to be done. Picture below shows the original TJA1103 chip type(left) and a new version(right) that should be replaced.
J38-2 is the reset pin of TJA1103. Connect it with an extended pin which can trace to a GPIO pin of daughter board. Provide J38-2 with a low pulse to reset TJA1103.
- Other tips for usage
- Before powering on, press the daughter board hard to make sure the connecters are tightly connected.
- The MDIO and MDC pins are not traced from daughter board to S32X-MB. External transceiver can be used to monitor the master/slave mode of TJA1103.
- Conclusion
Do not suggest customer using TJA1103 PHY on MB to test or develop project. Use the Realtek PHY on daughter board instead. If two switch ports are required, use S32E288-975 or S32Z280-400.
