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Chapter 33 Boot Assist Module (BAM)
MPC5602P Microcontroller Reference Manual, Rev. 4
826
Freescale Semiconductor
In case of flash with public access, the received password is compared with the public password
0xFEED_FACE_CAFE_BEEF.
If public access is not allowed but the flash is not secured, the received password is compared with the
value saved on NVPWD0 and NVPWD1 registers.
In uncensored devices, it is possible to download code via LINFlex or FlexCAN (serial boot mode) into
internal SRAM with any 64-bit private password stored in the flash and provided during the boot sequence.
In the previous cases, comparison is done by the BAM application. If it goes wrong, BAM pushes the
device into static mode.
In case of public access not allowed and flash secured, the password is written into SSCM[PWCMPH/L]
registers.
In case of flash secured with public access not allowed (user password configured in the NVPWD0 and
NVPWD1 registers), the user must set the swapped password: NVPWD1 and NVPWD0 to access the
device (refer to following examples).
Example 33-1.
In devices with flash secured, registers are programmed:
NVPWD0 = 0x87654321
NVPWD1 = 0x12345678
NVSCI0 = 0x55AA1111
NVSCI1 = 0x55AA1111
To download the code via SLB, the provided password is 0x1234_5678_8765_4321 (swapped
WITH respect to NVPWD0/NVPWD1 —> NVPWD1/NVPWD0).
Example 33-2.
In devices with flash NOT secured, registers are programmed:
NVPWD0 = 0x87654321
NVPWD1 = 0x12345678
NVSCI0 = 0x55AA55AA
NVSCI1 = 0x55AA55AA
To download the code via SLB the provided password is 0x8765_4321_1234_5678 (as expected
from NVPWD0/NVPWD1).
After a fixed time waiting, comparison is done by hardware. Then BAM again verifies the SEC flag in
SSCM_STATUS:
•
SEC = 0, flash is now unsecured and BAM continues its task
•
SEC = 1, flash is still secured because password was wrong; BAM puts the device into static mode.
This fixed time depends on external crystal oscillator frequency (XOSC). With XOSC of 12 MHz, fixed
time is 350 ms.