MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 16-11
Upon reception of either a valid CAN message with an ID equal to 0x011 and containing 8 bytes of data
or a valid eSCI message, the BAM moves to one of two serial boot submodes: either CAN serial boot mode
or eSCI serial boot mode.
In CAN serial boot mode, the eSCI_A signal RXD_A reverts to GPIO input. The ensuing download
protocol is assumed to be all on the CAN bus; eSCI messages are ignored.
In eSCI serial boot mode, the CAN_A signals CNRX_A and CNTX_A revert to GPIO inputs and the
TXD_A signal is configured as an output. The ensuing download protocol is assumed to be on the eSCI
bus and CAN messages are ignored.
16.3.2.3.3 CAN Serial Boot Mode Download Protocol
The download protocol follows 4 steps:
1. Download 64-bit password
2. Download start address and size of download
3. Download data
4. Execute code from start address
Table 16-8. Serial Boot Mode—Baud Rate and Watchdog Summary
Crystal
Frequency
(MHz)
System Clock
Frequency
(MHz)
SCI Baud Rate
(baud)
CAN Baud Rate
(baud)
Watchdog
Timeout period
(seconds)
f
xtal
f
sys
=1.5 * f
xtal
f
sys
/ 1250 f
sys
/ 60 2.5 * 2
27
/ f
sys
8 12 9600 200K 28.0
12 18 14400 300K 18.6
16 24 19200 400K 14.0
20 30 24000 500K 11.2
Table 16-9. CAN/eSCI Reset Configuration for CAN/eSCI Boot
Pins
Reset
Function
Initial Serial
Boot Mode
Serial Boot Mode after a
valid CAN message received
Serial Boot Mode after a
valid eSCI message received
CNTX_A GPIO CNTX_A CNTX_A GPIO
CNRX_A GPIO CNRX_A CNRX_A GPIO
TXD_A GPIO GPIO GPIO TXD_A
RXD_A GPIO RXD_A GPIO RXD_A
Table 16-10. CAN/eSCI Reset Pin Configuration
Pins I/O
Weak Pull-Up
State
Hysteresis
Driver
Configuration
Slew Rate
Input Buffer
Enable
CNTX_A /
TXD_A
Output Enabled/Up — Push/Pull Medium N
CNRX_A /
RXD_A
Input Enabled/Up Y — — —
GPIO Input Enabled/Up Y — — —
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