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Boot Assist Module (BAM)
MPC5566 Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor
16-17
16.3.2.3.4
eSCI Serial Boot Mode Download Process
The eSCI serial boot mode download process contains the following steps:
1. Download the 64-bit password.
2. Download the start address, VLE flag, and the number of data bytes to download.
3. Download the data.
4. Execute the code from start address.
Each step in the following process must complete before the next step starts. The eSCI operates in half
duplex mode where the host sends a byte of data, then waits for the echo back from the MCU before
proceeding with the next byte. Bytes sent from the host before the previous echo from the MCU is received
are ignored.
1. Download the 64-bit password.
The first 8 bytes of eSCI data the host computer sends must contain the 64-bit serial download
password. For each valid eSCI message received, the BAM transmits the same data on the eSCI A
TXDA signal.
The received 64-bit password is checked for validity. It is checked to ensure that none of the
4 x 16-bit halfwords are illegal passwords (0x0000 or 0xFFFF). A password must have at least one
0 and one 1 in each halfword to qualify as 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 censored and the password is compared
with a password stored in the shadow row of internal flash memory.
If Nexus is enabled, the MCU is not censored or is booting from external flash and the password
is compared to the constant value of 0xFEED_FACE_CAFE_BEEF.
If the password fails a validity test, the MCU stops responding to all stimulus. To repeat the boot
operation, assert the RESET signal or wait for the watchdog timer to reset the MCU. If the
password is valid, the BAM refreshes the e200z6 watchdog timer and proceeds to step 2.
2. Download the start address, VLE bit, and the download size.
The host computer must send the next eight bytes of eSCI data that contains:
— 32-bit start address in internal SRAM indicating where to store the succeeding data in memory;
— 32-bit number containing a 1-bit variable length encoded (VLE) flag followed by a 31-bit
length field that contains the number of data bytes to receive and store in memory before
switching to execute the code just loaded.
The start address is normally located on a word boundary (4-bytes), therefore the least significant
2 bits of the address are ignored. For each valid eSCI message received, the BAM transmits the
same data on the eSCI A TXDA signal.
Set the VLE bit in the serial download data (most significant bit in the LENGTH word) if the code
to download uses VLE instructions.
3. Download the data.
The host computer must then send a succession of eSCI messages, each containing raw binary data.
Each byte of data received is stored in the MCU’s memory, starting at the address specified in the
previous step and incrementing through memory until the number of data bytes received and stored
Summary of Contents for MPC5566
Page 81: ...Introduction MPC5566 Microcontroller Reference Manual Rev 2 1 24 Freescale Semiconductor...
Page 135: ...Signal Description MPC5566 Microcontroller Reference Manual Rev 2 2 54 Freescale Semiconductor...
Page 189: ...Reset MPC5566 Microcontroller Reference Manual Rev 2 4 20 Freescale Semiconductor...
Page 603: ...Flash Memory MPC5566 Microcontroller Reference Manual Rev 2 13 38 Freescale Semiconductor...
Page 609: ...SRAM MPC5566 Microcontroller Reference Manual Rev 2 14 6 Freescale Semiconductor...
Page 1073: ...MPC5566 Microcontroller Reference Manual Rev 2 22 36 Freescale Semiconductor...
Page 1185: ...Nexus MPC5566 Microcontroller Reference Manual Rev 2 25 92 Freescale Semiconductor...