MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor
16-13
NOTE
Internal SRAM is protected by 64 bit wide error correction coding hardware
(ECC). This means that any write to uninitialized internal SRAM must be
64 bits wide, otherwise an ECC error occurs. Therefore the BAM buffers
downloaded data until 8 bytes have been received then does a single 64 bit
wide write. Only internal SRAM supports 64 bit writes therefore attempting
to download data to other RAM apart from internal SRAM causes errors. If
the start address of the downloaded data is not on an 8 byte boundary, the
BAM writes 0x00 to the memory locations from the preceding 8 byte
boundary to the start address (maximum 4 bytes). The BAM also writes
0x00 to all memory locations from the last byte of data downloaded to the
following 8 byte boundary (maximum 7 bytes)
4. Execute code
The BAM waits for the last CAN message transmission to complete. Then the CAN controller is
disabled. CNTX_A and CNRX_A revert to GPIO inputs. Then the BAM switches execution to the
downloaded code by branching to the first address in which code is stored, as specified in step 2 of
the protocol.
NOTE
The code that is downloaded and executed must periodically refresh the
e200z6 watchdog timer or change the timeout period to a value that does not
cause resets during normal operation.
16.3.2.3.4
eSCI Serial Boot Mode Protocol
The download protocol follows four steps:
1. Download 64-bit password
2. Download start address and size of download
3. Download data
4. Execute code from start address
Table 16-11. CAN Serial Boot Mode Download Protocol
Protocol
Step
Host Sent Message
MCU Response
Message
Action
1
CAN ID 0x011 + 64-bit
password
CAN ID 0x001
+ 64-bit password
Password checked for validity and compared against
stored password. e200z6 Watchdog timer is
refreshed if the password check is successful
2
CAN ID 0x012 + 32-bit
store a 32-bit
number of bytes
CAN ID 0x002
+ 32-bit store address
+ 32-bit number of bytes
Load address and size of download are stored for
future use
3
CAN ID 0x013
+ 8 to 64 bits of raw binary
data
CAN ID 0x003
+ 8 to 64 bits of raw
binary data
Each byte of data received is store in MCU memory,
starting at the address specified in the previous step
and incrementing until the amount of data received
and stored, matched the size as specified in the
previous step.
4
None
None
The BAM program returns I/O pins and CAN module
to their reset state, then branches to the first address
the data was stored to (As specified in step 2)
Summary of Contents for MPC5553
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