L-Bus to U-Bus Interface (L2U)
MPC561/MPC563 Reference Manual, Rev. 1.2
11-4
Freescale Semiconductor
When a load to or store from the U-bus resource is issued by the RCPU, it is compared against the DMPU
region access (address and attribute) comparators. If none of the access attributes are violated, the access
is directed to the U-bus by the L2U module. If the DMPU detects an access violation, it informs the error
status to the master initiating the cycle.
When show cycles are enabled, accesses to all of the L-bus resources by the RCPU are made visible on
the U-bus side by the L2U.
The L2U is responsible for handling the effects of reservations on the L-bus and the U-bus. For the L-bus
and the U-bus, the L2U detects reservation losses and updates the RCPU core with the reservation status.
11.4.2
Reset Operation
While hard or soft reset is asserted on the U-bus, the L2U asserts the corresponding L-bus reset signals.
Upon soft reset assertion, the L2U goes to an idle state and all pending accesses are ignored. Additionally,
the L2U module control registers are not initialized on soft reset, keeping the system configuration
unchanged.
Upon assertion of hard reset, the L2U control registers are initialized to their reset states. The L2U also
drives the reset configuration word from the U-bus to the L-bus upon hard reset.
11.4.3
Peripheral Mode
In the peripheral mode of operation the RCPU is shut down and an alternative master on the external bus
can perform accesses to any internal bus (U-bus and L-bus) slave.
The external master can also access the internal MPC500 special registers that are located in the L2U
module. In order to access one of these MPC500 registers the EMCR[CONT] bit in the USIU must be
cleared.
11.4.4
Factory Test Mode
Factory test mode is a special mode of operation that allows access to the internal modules for testing. This
mode is not intended for general use and is not supported for normal applications.
11.5
Data Memory Protection
The data memory protection unit (DMPU) in the L2U module provides access protection for the memory
regions on the U-bus side from load/store accesses by the RCPU. (Only U-bus space is protected.) The
DMPU does not protect MPC500 register accesses initiated by the RCPU on the L-bus. The user can assign
up to four regions of access protection attributes and can assign global attributes to any space not included
in the active regions. When it detects an access violation, the L2U generates an exception request to the
CPU. A functional diagram of the DMPU is shown in
.
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...