OK335xS 系统启动配置解析
一、参考文档：
AM335x ARM® Cortex™-A8 Microprocessors (MPUs) Technical Reference Manual
二、SYSBOOT Configuration Pins Notes(page 4111):
1. WAIT is monitored on GPMC_WAIT0.
2. MUX1 and MUX2 designate which group of XIP signals are used. Each group is defined in Table 26-9.
3. Note that even though some bits may be a "don't care" for ROM code, all SYSBOOT values are latched into the CONTROL_STATUS register and may be used by software after ROM execution has completed.
4. SYSBOOT[15:0] terminals are respectively LCD_DATA[15:0] inputs, latched on the rising edge of PWRONRSTn.
LCD_DATA[15:0]引脚电平在PWRONRSTn上升沿的时候被锁定进入SYSBOOT[15:0]
三、Current Configuration:
1. SYSBOOT[15:0]: 0b0100 0000 1000 0100
2. 参考表格：Table 26-7. SYSBOOT Configuration Pins[4](page 4106)
3. 分析配置：
+--------+----------------+----------------+----------------+---------------+
| Bits | SYSBOOT[15:14] | SYSBOOT[13:12] | SYSBOOT[11:10] | SYSBOOT[9] |
+--------+----------------+----------------+----------------+---------------+
| value | 01 | 00 | 00 | 0 |
+--------+----------------+----------------+----------------+---------------+
| mode | 01b = 24MHz | reserved |non-muxed device|ECC done by ROM|
+--------+----------------+----------------+----------------+---------------+
| Bits | SYSBOOT[8] | SYSBOOT[7:6] | SYSBOOT[5] | SYSBOOT[4:0] |
+--------+----------------+----------------+----------------+---------------+
| value | 0 | 10 | 0 | |
+--------+----------------+----------------+----------------+ |
| mode | 8-bit device | Don't care |CLKOUT1 disabled| |
+--------+----------------+----------------+----------------+ |
| Bits | Boot Sequence | |
+--------+--------------------------------------------------+ |
| value | 00100 |
+--------+------------------------------------------------------------------+
| mode | 1.UART0 2.XIP 3.MMC0 4.NAND |
+--------+------------------------------------------------------------------+
