NXP Semiconductors MPC5644A, Reference Manual, Page: 637 / 1735

Boot Assist Module (BAM)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 637
21.5.6 Booting from the External Bus Interface (EBI)
For devices packaged in the 324-ball BGA or chip scale packages (CSP), there is an option to boot from
a memory device on the external bus. Drive the BOOTCFG0 high to select serial boot mode.
NOTE
For serial boot the user needs to connect a boot memory device with a
programmed valid RCHW to the EBI.
The BAM program sets up the MMU entries for EBI and Internal Flash (see Table 21-11 ), EBI bus pins
and tries to read RCHW from logical address 0x2000_0000.
If the valid RCHW is read from that address, the BAM program reads user application code start address
from logical address 0x2000_0004, parses RCHW, sets up watchdogs, updates EBI, SRAM and Internal
Flash MMU entries, according the RCHW[VLE] bit and passes control to the user code.
If no valid RCHW was read, BAM switches to the serial boot mode.
21.5.6.1 EBI Configuration for External Bus Interface Boot Mode
The BAM program sets up EBI related registers as shown in Table 21-12 .
Table 21-11. MMU Configuration for EBI Boot and Serial Boot modes
TLB
Entry
Region
Logical
Base Address
Physical
Base Address
Size Attributes
1 Internal Flash 0x0000_0000 0x2000_0000 16 Mbytes Not guarded
Big endian
Global PID
2 EBI 0x2000_0000 0x2000_0000 16 Mbytes Not guarded
Big endian
Global PID
Table 21-12. EBI register settings
Register Value Comments
EBI_MCR 0x0000_0801 16-bit wide bus
EBI_BR0 0x2000_0803 Burst Inhibit
EBI_OR0 0xFF80_00F0 Set 15 wait states, 8 MB
SIU_PCR0 0x443 Selects CS[0] function, sets pad to 20 pF drive strength,
enables weak pull device for pad and enables pullup
SIU_PCR[8:11] 0x440 Selects ADDR[12:15] and sets pads to 20 pF drive
strength
SIU_PCR[12:27] 0x40C Selects ADDR[16:31], sets pads to medium slew rate
and enables weak pull device for pads
SIU_PCR[28:43] 0x440 Selects DATA[0:15] and sets pads to 20 pF drive
strength