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Boot Assist Module (BAM)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
633
2. Host sends start address, size of download code in bytes, and VLE bit.
3. Host sends the application code data.
4. The device switches to the loaded code at the start address.
The communication is done in half-duplex manner, any transmission from host is followed by the device
transmission. The host computer should not send data until it receives echo from the device. All multibyte
data structures have to be sent most significant byte (MSB) first.
When the CAN is used for serial download, the data is packed into standard CAN messages in the
following manner:
•
A message with 0x11 ID and 8-byte length is used to send the password. The device transmits the
same data, but the message ID is set to 0x1.
•
A message with 0x12 ID and 8-byte length is used to send the start address, length, and the VLE
mode bit. The device transmits back the same data, but with ID set to 0x2.
•
Messages with 0x13 ID are used to send the downloaded data. The device transmits back received
data with message ID of 0x3.
When the SCI is used for serial download, the data has to be sent on a byte-by-byte basis. the device
transmits back the received data.
21.5.5.4
Download protocol execution
The BAM program executes the serial boot as follows:
1. Download 64-bit password.
The received 8-byte password is checked for validity. For a password to be valid, none of its four
16-bit half words must equal 0x0000 or 0xFFFF.
The BAM program then checks the censorship status of the device by checking the bit
SIU_CCR[DISNEX]. If Nexus is disabled, the device 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 device is not considered to be censored and the password is compared to
the fixed value = 0xFEED_FACE_CAFE_BEEF.
If the password check fails, the device stops responding. To get the device out of that state, the
RESET signal must be asserted.
If the password check passes, the BAM transitions to the next step in the protocol.
2. Download start address, size of download, and VLE bit.
The next 8 bytes received by the device are considered to contain a 32-bit start address, the VLE
mode bit, and a 31-bit code length (see
Summary of Contents for MPC5644A
Page 2: ...MPC5644A Microcontroller Reference Manual Rev 6 2 Freescale Semiconductor...
Page 24: ...MPC5644A Microcontroller Reference Manual Rev 6 24 Freescale Semiconductor...
Page 26: ...MPC5644A Microcontroller Reference Manual Rev 6 26 Freescale Semiconductor...
Page 52: ...Introduction MPC5644A Microcontroller Reference Manual Rev 6 52 Freescale Semiconductor...
Page 56: ...Memory Map MPC5644A Microcontroller Reference Manual Rev 6 56 Freescale Semiconductor...
Page 1228: ...Decimation Filter MPC5644A Microcontroller Reference Manual Rev 6 1228 Freescale Semiconductor...
Page 1440: ...FlexCAN Module MPC5644A Microcontroller Reference Manual Rev 6 1440 Freescale Semiconductor...