MPC555
/
MPC556
L-BUS TO U-BUS INTERFACE (L2U)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
11-2
• Supports a default global entry for memory space not covered by other regions:
— Default access protection
— Default guarded attribute
• Interrupt generated upon:
— Access violation
— Load from guarded region
— Write to read-only region
• The PowerPC MSR[DR] bit (data relocate) controls DMPU protection on/off op-
eration
• Programming is done using PowerPC’s
mtspr/mfspr
instructions to/from imple-
mentation specific special purpose registers.
• No protection for accesses to the SRAM module on the L-bus (SRAM has its own
protection options)
11.3 L2U Block Diagram
shows a block diagram of the L-bus to U-bus interface.
Figure 11-1 L2U Bus Interface Block Diagram
11.4 Modes Of Operation
The L2U Module can operate in the following modes:
• Normal Mode
• Reset Operation
• Factory Test Mode
• Peripheral Mode
U-bus Interface
L-bus Interface
U-bus
Address
Decode
Reservation
Control
DMPU
L-bus
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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