Boot mode
When the processor reset, AM335x internal logic will boot form ROM code, then reads SYS_BOOT configuration pin level state to identify which mode to select. SYS_BOOT[15:0] is pin multiplexing with LCD_DATA[15:0].
Figure 4-7 SYS_BOOT config sch
Default, MCC-AM335X-Y have two mode, if left there as a NO connect, AM335x will boot from NAND first, Failure to respond will try I2C, SPI0, EMAC1. If pull SYS_BOOT3 the UP, there will try MMC1-> MMC0-> UART0-> USB0.
| BOOT MODE | SYS_BOOT[4:0] | SYS_BOOT[4:0] | SYS_BOOT[4:0] | SYS_BOOT[4:0] | SYS_BOOT[4:0] |
|---|---|---|---|---|---|
| NAND->I2C->SPI0->EMAC1 | 1 | 0 | 1 | 0 | 0 |
| MMC1->MMC0->UART0->USB0 | 1 | 1 | 1 | 0 | 0 |
Table 4-2 Default mode
See the TI Datasheet for complete mode, if you need other mode, change the resistor by Figure 4-7.