PXS20RM Datasheet, PDF (144/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Boot Assist Module (BAM)
8.3 Memory map
The BAM code resides in 8 KB of ROM mapped from address 0xFFFF_C000. The address space and
memory used by the BAM is shown in Table 8-1.
Table 8-1. BAM memory organization
Entity
BAM entry point
RAM area used by the BAM code (do not use)
Downloaded code base address
Address
0xFFFF_C000
0x4000_0000–0x4000_00FF
0x4000_0100
The RAM location where to download the code can be any 4 byte-aligned location in the SRAM starting
from the address 0x4000_0100.
CAUTION
Do not use the RAM area used by the BAM code as indicated in Table 8-1.
8.4 Functional description
8.4.1 Entering boot modes
The PXS20 detects the boot mode based on external pins and device status. The following sequence
applies (see Figure 8-1):
1. To boot either from FlexCAN or LINFlex, the device must be forced into an Alternate Boot Loader
Mode via the FAB (Force Alternate Boot Mode) pin which must be asserted before initiating the
reset sequence. The type of alternate boot mode is selected according to the ABS (Alternate Boot
Selector) pins (see Table 8-2).
2. If FAB is not asserted, the device boots from the first flash memory sector which contains a valid
boot signature.
3. If no flash memory sector contains a valid boot signature, the device will go into static mode.
PXS20 Microcontroller Reference Manual, Rev. 1
8-2
Freescale Semiconductor