Freescale Semiconductor MPC5565, Reference Manual

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Boot Assist Module (BAM)
MPC5565 Microcontroller Reference Manual, Rev. 1.0
Freescale Semiconductor 15-7
15.3.2.1.1 Finding 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 15-4 .
If the BAM fails to find a valid RCHW, it assumes the flash is erased or corrupt and switches to serial-boot
If the value in RCHW is valid, the watchdog timer is enabled by setting the RCHW[WTE] bit, the BAM
program fetches the reset vector from BOOT_BLOCK_A 0x0004, and branches to the reset
boot vector. The application must have a valid instruction at the reset boot vector address.
BOOT_BLOCK_A 0x0000_0004
If the watchdog timer is enabled, the watchdog timeout is set to 2.5
×
2
17
system clock periods.
15.3.2.2 External Boot Modes
Use external boot mode to boot an application from an external asynchronous memory device that is
connected to the EBI. External boot mode is controlled by CS[0].
15.3.2.2.1 External Boot MMU Configuration
As shown in Table 15-5 , the BAM program sets up two MMU regions differently than in internal flash
boot mode (refer to Table 15-2 ). The internal flash logical addresses are mapped to the physical addresses
of the EBI.
Table 15-4. 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
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
A16 A17 A18 A19 A20 A21 A22 A23 A24 A25 A26 A27 A28 A29 A30 A31
Figure 15-4. Reset Boot Vector