Please follow the below procedure to boot BF609 from UART.
1. Please download LDRviewer from the below link www.dolomitics.com/.../ldrviewer_12.zip
2. Connect USB to UART cable from PC to BF609 board and power on the board.
3. Change the boot mode to Uart slave (boot SW position 7).
4. Open LdrViewer, then click File > Open > Choose the .ldr file(use attached simple application).
5. Select Tools > Uart boot.
6. In the Uart boot window, select COM port and bit rate(115200).
7. Click Test Port and it will ask us to reset hardware, press reset switch in BF609 board.
8. Click Autobaud, the slave acknowledge host with four bytes of hex data in Receive(hex) tab. The acknowledgment consists of 4 bytes: 0xBF, UART_CLK [15:8], UART_CLK [7:0], 0x00.
9. Click Send DXE.
Once the DXE sent, the "UART boot" window indicates as “done” and the board starts booting.
Please close the LDRviewer once it shows “done”.