NXP Semiconductors MPC5566, Reference Manual

Page: 666 / 1268

Boot Assist Module (BAM)
MPC5566 Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 16-7
The BAM program continues to make specific initialization in one of the four boot modes.
16.3.2.1 Internal Boot Mode
When the BAM detects internal flash boot mode, a bus error exception handler is invoked to handle corrupt
data from internal flash memory and avoid a bus error. The BAM program reads up to six addresses in
internal flash to find a valid 16-bit reset configuration halfword (RCHW). If a valid RCHW is read, the
BAM program sets the e200z6 watchdog timer enable bit RCHW[WTE]. If a valid RCHW is not read, the
BAM program proceeds to serial boot mode.
16.3.2.1.1 Finding the Reset Configuration Halfword
A valid RCHW is a 16-bit value that contains a constant 8-bit boot identifier and configuration bits (refer
to
Section 4.4.3.5.1, “Reset Configuration Halfword Definition ”). The RCHW is the first halfword in one
of the six low address flash blocks as shown in Table 16-4 .
If the BAM fails to find a valid RCHW, it assumes the flash is erased or corrupt and switches to serial boot
operating mode.
Address: 0x00FF_FDDC Value: 0xCAFE
MSB
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
Binary value 1 1 0 0 1 0 1 0 1 1 1 1 1 1 1 0
Hex value C A F E
Address: 0x00FF_FDDE Value: 0xBEEF
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
Binary value 1 0 1 1 1 1 1 0 1 1 1 0 1 1 1 1
Hex value B E E F
Figure 16-3. Serial Boot Flash Password
Table 16-4. Low Address Space (LAS)
Block Memory Addresses
Block Address
0 0x0000_0000
1 0x0000_4000
2 0x0001_0000
3 0x0001_C000
4 0x0002_0000
5 0x0003_0000