External Bus Interface
MPC561/MPC563 Reference Manual, Rev. 1.2
9-36
Freescale Semiconductor
illustrates the internal finite-state machine that implements the arbiter protocol.
Figure 9-27. Internal Bus Arbitration State Machine
Table 9-4. Priority Between Internal and External Masters over External Bus
1
1
External master will be granted external bus ownership if EARP is greater than the internal access priority.
Type
Direction
Priority
Parked access
2
2
Parked access is instruction or data access from the RCPU which is initiated on the internal bus without
requesting it first in order to improve performance.
Internal
→
external
0
Instruction access
Internal
→
external
3
Data access
Internal
→
external
4
External access
external
→
external/internal
EARP (could be programmed to 0 – 7)
IDLE
BG = 1
BB = three
External
BG = 0
External Master
BR
=
0
External Master
Release Bus
BG = 1
BB = three
BB = three
BB = 0
BG = 1
BB = 0
BB = 1
B
B
=
1
, B
R
=1
BR = 0
Requests Bus
BR = 1
External Device With Higher
Priority than the Current Internal
Bus Master Requests the Bus
Internal Master With Higher
Priority than the External Device
Requires the Bus
MCU Needs
No Longer
the Bus
Needs the Bus
Still Needs
the Bus
Wait
Device Owner
Owner
Bus
MPC500
MPC500 Device
MPC500 Device
MPC500 Device
state
state
state
MPC500
Device
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...