Boot Assist Module (BAM)MPC5566 Microcontroller Reference Manual, Rev. 2Freescale Semiconductor 16-1116.3.2.2.5 Read the Reset Configuration HalfwordThe BAM program reads the first location in external memory, i.e address 0x2000_0000, for a valid resetconfiguration halfword (RCHW, refer to Figure 16-4). If the BAM program finds a valid RCHW, thefollowing occurs:• The CS[0] port size and data pins are configured according to the RCHW[PS0] bit• The e200z6 core watchdog timeout is enabled or disabled using the RCHW[WTE] bit.The watchdog timeout interval is 2.5 × 217 system clock periods when using the RCHW.• MMU boots using PowerPC Book E code or Freescale VLE code according to the RCHW[VLE]setting.Then the BAM program reads the reset vector shown in Figure 16-4 from the address 0x2000_0004 andbranches to that reset vector address, starting application program execution.16.3.2.3 Serial Boot Mode OperationSerial boot operating mode configures:• FlexCAN A and the eSCI A GPIO signals• Unused message buffers in FlexCAN A are designated as scratch pad SRAM• Flash memory map unit (MMU) TLB entries• Watchdog timer is enabled and set to 2.5 × 227 system clock cyclesSerial boot mode downloads:• 64-bit password• 32-bit start address• 32-bit download consisting of a 1-bit VLE flag followed by a 31-bit length fieldSet the VLE flag to 1 for devices that support variable length encoding and must run in VLE mode. Whenthe VLE flag is set, the BAM configures these components:• External bus interface (EBI) signals and port size• SRAM structure• VLE attribute is set in flash memory map unit (MMU) TLB entries 1, 2, and 3Clear the VLE bit to 0 for devices that use the PowerPC Book E or Power Architecture instruction setmode.16.3.2.3.1 Serial Boot Mode MMU and EBI ConfigurationThe BAM program sets up the MMU for all peripheral and memory regions in one of two different modesand sets up the EBI in one of three different modes; depending on how serial boot mode was entered.If serial boot mode is entered directly by choosing the mode with the BOOTCFG signals, or was enteredindirectly from internal boot mode because no valid RCHW was found, then the MMU is configured thesame way as for internal boot mode. The EBI is disabled and all bus pins function as GPIO.
