SCI_Boot
Enable the SCI-A clock
set the LSPCLK to /4
functionality and pullups on
Enable the SCIA TX and RX pin
Setup SCI-A for
1 stop, 8-bit character,
no parity, use internal
SC clock, no loopback,
disable Rx/Tx interrupts
Disable SCI FIFOs
Prime SCI-A baud register
Enable autobaud detection
Autobaud
lock
?
No
Yes
Echo autobaud character
Read KeyValue
Yes
No
Valid
KeyValue
(0x08AA)
?
Return
FLASH_ENTRY_POINT
Read and discard 8
reserved words
Read EntryPoint address
Call CopyData
EntryPoint
Return
Set GetWord function pointer
to SCIA_GetWordData
TX and RX
SCI_Boot Function
At higher baud rates, the slew rate of the incoming data bits can be effected by transceiver and connector
performance. While normal serial communications may work well, this slew rate may limit reliable
auto-baud detection at higher baud rates (typically beyond 100kbaud) and cause the auto-baud lock
feature to fail. To avoid this, the following is recommended:
1. Achieve a baud-lock between the host and 28x SCI bootloader using a lower baud rate.
2. Load the incoming 28x application or custom loader at this lower baud rate.
3. The host may then handshake with the loaded 28x application to set the SCI baud rate register to the
desired high baud rate.
Figure 2-11. Overview of SCI_Boot Function
34 Bootloader Features SPRU722C – November 2004 – Revised October 2006
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