PXR40RM Datasheet, PDF (288/1434 Pages) Freescale Semiconductor, Inc – PXR40 Microcontroller

Boot Assist Module (BAM)
9.5.3.1 Application Start Address Register
Application Start Address Register (Figure 9-5) is the 32-bit word after the RCHW in the application code
memory device (internal or external flash). The BAM uses the value from this location as a start address
of the user application to pass control to.
BOOT_BLOCK_ADDRESS + 0x0000_0004
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 9-5. Application Start Address Register
9.5.4 Internal Boot Mode
When the BAM program detects internal flash boot mode, the BAM:
1. Configures a machine check exception handler, since it will be accessing flash memory locations
that may be corrupted and cause a bus error
2. Searches for a valid RCHW in six pre-defined locations, as shown in Table 9-6
Table 9-6. Possible RCHW Locations in the Internal Flash
Block
Address
0
0x0000_0000
1
0x0000_4000
2
0x0001_0000
3
0x0001_C000
4
0x0002_0000
5
0x0003_0000
3. If a valid RCHW is not found, the BAM program switches to serial boot mode
4. If the BAM program finds a valid RCHW:
— BOOT_BLOCK_ADDRESS is the address (from Table 9-6) of the valid RCHW
— The BAM program fetches the application start address from
BOOT_BLOCK_ADDRESS + 0x4
— The BAM branches to this start address (shown in Figure 9-5)
— The core watchdog is enabled (if RCHW[WTE] = 1) and/or SWT is disabled (if
RCHW[SWT] = 0)
— The MMU TLB entries 1,2,3 are programmed with VLE attribute if the RCHW[VLE] = 1.
9.5.5 Serial Boot Mode
When serial boot mode is detected, either because of the BOOTCFG configuration or because a valid
RCHW word was not found in any of the expected locations in the Flash, the BAM program does the
following:
PXR40 Microcontroller Reference Manual, Rev. 1
9-8
Freescale Semiconductor