L-Bus to U-Bus Interface (L2U)
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
11-11
2. Latches the address and the data of the L-bus access, along with all address attributes
3. Waits for the termination of the L-bus access and latches the termination status (data error)
4. Arbitrate for the U-bus, and when granted, starts the U-bus access, asserting show cycle request on
the U-bus, along with address, attributes and the write data. The L2U module provides address
recognition and acknowledgment for the address phase. If the no-show cycle indicator from the
U-bus is asserted, the L2U does not start the show cycle. The L2U module releases the U-bus until
the no-show cycle indicator is negated and then arbitrates for the U-bus again.
5. When the L2U module has U-bus data bus grant, it drives the data phase termination handshakes
on the U-bus.
6. Releases the L-bus
11.7.5
L-Bus Read Show Cycle Flow
The L2U performs the following sequence of actions for an L-bus read show cycle.
1. Arbitrates for the L-bus to prevent any other L-bus cycle from starting
2. Latches the address of the L-bus access, along with all address attributes
3. Waits for the data phase termination on the L-bus and latches the read data, and the termination
status from the L-bus
4. Arbitrates for the U-bus, and when granted, starts the U-bus access, asserting the show cycle
request on the U-bus, along with address attributes. The L2U module provides address
recognition/acknowledgment for the address phase. If the no-show cycle indicator from the U-bus
is asserted, the L2U does not start the show cycle. The L2U module releases the U-bus until the
no-show cycle indicator is negated and then arbitrates for the U-bus again.
5. When the L2U module has U-bus data bus grant, it drives the read data and the data phase
termination handshakes on the U-bus
6. Release the L-bus.
11.7.6
Show Cycle Support Guidelines
The following are the guidelines for L2U show cycle support:
•
The L2U module provides address and data for all qualifying L-bus cycles when the appropriate
mode bits are set in the L2U_MCR.
•
The L2U-module-only provides show cycles L-bus activity that is not targeted for the U-bus or the
L2U module internal registers, regardless of the termination status of such activity.
•
The L2U module does not provide show cycle access to any MPC500 special purpose register.
•
The L2U does not start a show cycle for an L-bus access that is retried. This decision to not start
the show cycle causes a clock delay before the cycle can be retried, since the L2U module will have
arbitrated away the L-bus immediately on detecting the show cycle, before the retry information is
available.
•
The L2U module does not show cycle any L-bus activity that is aborted.
•
The L2U module does not access the U-bus if the USIU inhibits show cycle activity on the U-bus.
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...