PXS20RM Datasheet, PDF (154/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Boot Assist Module (BAM)
After performing the autobaud measurement and setting up the baud rate, the corresponding RX input is
reconfigured and the related standard download process is started; in case of a detected CAN transmission
a download using the CAN protocol as described in Section 8.4.4, CAN Boot — autobaud disabled, and
in case of a detected UART transmission a download using the UART protocol as described in
Section 8.4.3, UART Boot — autobaud disabled.
The following Figure 8-6 identifies the corresponding flow and steps.
Determine clock frequency
of external oscillator
Program PLL accordingly
Falling edge
at FlexCAN RX
?
detected
Falling edge
at LINFlex RX
?
detected
Autobaud measurement
for FlexCAN
Set matching baud rate / FlexCAN
Continue with CAN download
Autobaud measurement
for LINFlex
Set matching baud rate / LINFlex
Continue with UART download
Figure 8-6. Autobaud configuration and detection/measurement flow
8.4.5.2 Autobaud measurement for LINFlex / UART protocol
Enabling the autobaud feature when using the UART protocol assumes that first an additional byte is sent
from host to MCU. Its value is 0x00, resulting in a high - low - high transition visible on the UART RX pin.
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PXS20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor