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MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
16-12
Freescale Semiconductor
Each step must complete before the next step starts.
1. Download 64-bit password
The host computer must send a CAN message with ID = 0x011 and containing the 64-bit serial
download password. CAN messages with other IDs or fewer bytes of data are ignored. When a
valid message has been received, the BAM transmits a CAN message using ID = 0x001 and
containing the data received. The host should not send a second CAN message until the echo of the
first message has been received. A CAN message sent before the echo is received is ignored.
The received 64-bit password is checked for validity. It is checked to ensure that none of the 4 x
16-bit halfwords are 0x0000 or 0xFFFF. These are considered illegal passwords. A password must
have at least one 0 and one 1 in each halfword lane to be considered legal.
The BAM program then checks the censorship status of the MCU by checking the DISNEX bit in
the SIU_CCR. If Nexus is disabled, the MCU is considered to be censored and the password is
compared with a password stored in the shadow row in internal flash memory.
If Nexus is enabled, the MCU is considered to be not censored or booting from external flash and
the password is compared to the fixed value = 0xFEED_FACE_CAFE_BEEF.
If the password fails any of these validity tests, the MCU stops responding to all stimulus. To repeat
boot operation the MCU needs to be reset by external reset or by watchdog. If the password is valid,
the BAM program refreshes the e200z6 watchdog timer and the next step in the protocol can be
performed.
2. Download start address and size of download
The host computer must send a CAN message with ID = 0x012 and containing a 32 bit address in
internal SRAM, indicating where the following data should be stored in the memory map of the
MCU; and a 32 bit number indicating how many bytes of data are to be received and stored in
memory before switching to execute the code just loaded. The start address is assumed to be on a
word boundary (4 bytes), therefore the least significant 2 bits of the address are ignored. CAN
messages with other IDs or fewer bytes of data are ignored. When a valid message has been
received, the BAM transmits a CAN message using ID = 0x002 and containing the data received.
The host should not send a another CAN message until the echo of the previous message has been
received by the host. A CAN message sent before the echo is received is ignored.
3. Download data
The host computer must send a succession of CAN messages with ID = 0x013 (The data length is
variable) and containing raw binary data. Each byte of data received is stored in the MCU’s
memory, starting at the address specified in the previous protocol step and incrementing through
memory until the number of bytes of data received and stored in memory matches the number
specified in the previous protocol step. CAN messages with other IDs are ignored. When a valid
message has been received, the BAM transmits a CAN message using ID = 0x003 and containing
the data received. The host should not send another CAN message until the echo of the previous
message has been received by the host. A CAN message sent before the echo is received is ignored.
Содержание MPC5553
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