使用esp32外接lan8720模块做ethernet，编译后报错的原因？

我使用esp32外接lan8720模块做ethernet。使用esp-idf-release-v3.2的Ethernet示例代码进行编译。clock信号使用的是lan8720模块上的50MHz晶振，nINT/REFCLKO引脚与gpio0连接，模式选择为Ethernet PHY Clock Mode (GPIO0 Input) 。编译后报错E (1301) emac: Reset EMAC timeout。
具体log如下：
I (0) cpu_start: App cpu up.I (232) heap_init: Initializing. RAM available for dynamic allocation:I (239) heap_init: At 3FFAE6E0 len 00001920 (6 KiB): DRAMI (245) heap_init: At 3FFB4090 len 0002BF70 (175 KiB): DRAMI (251) heap_init: At 3FFE0440 len 00003AE0 (14 KiB): D/IRAMI (257) heap_init: At 3FFE4350 len 0001BCB0 (111 KiB): D/IRAMI (264) heap_init: At 40089B48 len 000164B8 (89 KiB): IRAMI (270) cpu_start: Pro cpu start user codeI (288) cpu_start: Starting scheduler on PRO CPU.I (0) cpu_start: Starting scheduler on APP CPU.I (291) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSEE (1301) emac: Reset EMAC Timeout
请教大神这是什么原因导致的，我该怎么做？谢谢！