External Bus Interface
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
9-33
Figure 9-24. Bus Arbitration Flowchart
9.5.7.1
Bus Request
The potential bus master asserts BR to request bus mastership. BR should be negated as soon as the bus is
granted, the bus is not busy, and the new master can drive the bus. If more requests are pending, the master
can keep asserting its bus request as long as needed. When configured for external central arbitration, the
MPC561/MPC563 drives this signal when it requires bus mastership. When the internal on-chip arbiter is
used, this signal is an input to the internal arbiter and should be driven by the external bus master.
9.5.7.2
Bus Grant
The arbiter asserts BG to indicate that the bus is granted to the requesting device. This signal can be
negated following the negation of BR or kept asserted for the current master to park the bus.
When configured for external central arbitration, BG is an input signal to the MPC561/MPC563 from the
external arbiter. When the internal on-chip arbiter is used, this signal is an output from the internal arbiter
to the external bus master.
Requesting Device
Arbiter
Request the Bus
1. Assert
BR
Terminate Arbitration
1. Negate
BG
(or keep asserted to park
1. Wait for
BB
to be negated.
3. Negate
BR
bus master
Operate as Bus Master
1. Perform data transfer
Release Bus Mastership
1. Negate
BB
Acknowledge Bus Mastership
2. Assert
BB
to become next master
Grant Bus arbitration
1. Assert
BG
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...