PXN20RM Datasheet, PDF (263/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller

Boot Assist Module (BAM)
NRZ signal
SYNC_SEG
Time segment 1
Time segment 2
1
Time quanta
7
Time quanta
2
Time quanta
1 bit time
Transmit point
1 time quanta = 4 system clock periods
Sample point
Figure 9-5. FlexCAN Bit Timing
The eSCI is configured for one start bit, eight data bits, no parity, and one stop bit. It operates at a
baud rate = system clock / 832. (See Table 9-6 for baud rate examples.)
NOTE
The BAM program during the serial download routine reconfigures the
software watchdog timer timeout (SWT_TO) from a default of 0x2_7100 to
0x800_0000. The SWT is always clocked from the 16 MHz IRC.
The BAM program ignores eSCI errors. All received data is assumed to be good and is echoed out on the
TXD_A signal.
Table 9-6. Serial-Boot Mode—Baud Rates
Crystal
Frequency
(MHz)
f_extal
8
12
16
20
40
SCI Baud Rate CAN Baud Rate
(baud)
(baud)
f_extal / 832
9600
14400
19200
24000
48000
f_extal / 40
200K
300K
400K
500K
1M
Upon reception of a valid CAN message with ID = 0x011 that contains 8 bytes of data, or an eSCI byte,
the BAM program transitions to one of two serial boot sub-modes: CAN serial-boot mode or eSCI
serial-boot mode.
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
9-9