External Bus Interface (EBI)
MPC5565 Microcontroller Reference Manual, Rev. 1.0
Freescale Semiconductor
12-61
12.5
Initialization and Application Information
12.5.1
Booting from External Memory
The EBI block does not support booting directly to external memory (i.e. fetching the first instruction after
reset externally). The MCU uses an internal boot assist module, which executes after each reset. The BAM
code performs basic configuration of the EBI block, allowing for external boot if desired. Refer to
Section 15.1.3, “Modes of Operation
,” for detail information about the boot modes supported by the MCU;
booting is not possible from external memory on the calibration bus.
If code in external memory needs to write EBI registers, this must be done in a way that avoids modifying
EBI registers while external accesses are being performed, such as the following method:
•
Copy the code that is doing the register writes (plus a return branch) to internal SRAM
•
Branch to internal SRAM to run this code, ending with a branch back to external flash
12.5.2
Running with SDR (Single Data Rate) Burst Memories
This includes FLASH and external SRAM memories with a compatible burst interface. BDIP is required
only for some SDR memories.
shows a block diagram of an MCU connected to a 32-bit SDR
burst memory.
Figure 12-43. MCU Connected to SDR Burst Memory
Refer to
for an example of the timing of a typical burst read operation to an SDR burst
memory. Refer to
for an example of the timing of a typical single write operation to SDR
memory.
CLKOUT
CS[0]
TS
WE/BE[0]
ADDR[8:29]
DATA[0:31]
BDIP
OE
MCU
CK
CE
ADV
BAA*
WE**
A[0:21]
D[0:31]
OE
SDR burstable
flash or SRAM
* Connection depending on the type of memory.
Flash memories typically use one WE signal as shown, RAMs use 2 or 4 (16-bit or 32-bit).
**
CAL_CS[0] ***
*** Not available on all devices, refer to the Signals chapter.
4M x 32
Содержание MPC5565
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