MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
E-1
Appendix E
Memory Access Timing
lists all possible memory access timings for internal and external memory combinations. The
clock values show the number of clocks from the moment an address is valid on a specific bus, until data
is back on that same bus. The following assumptions were used when compiling the information:
•
The arbitration time was ignored. The values assume that the bus (or buses) involved in a
transaction was in the IDLE state when the transaction needs that bus.
•
The UIMB works in a mode of 1:1. This is relevant for IMB access values. In the case of 2:1 mode,
the clock latency for a cycle on the IMB should be doubled (each IMB access takes two clocks).
•
The basic delay of an external bus to a U-bus is four clocks (external master case).
•
All IMB accesses are assumed to be 16-bit accesses only. If 32-bit accesses are used, then each such
IMB access is split into two separate 16-bit cycles with normal IMB performance for each.
Table E-1. Memory Access Times Using Different Buses
Internal Buses
External RAM/Flash
Show Cycle
Flash
RAM
DECRA
M
IMB
SIU
Internal
Memory
Mapped
External
Non-mappe
d Internal
Memory
Write Read
RCPU Load/Store
3/4
1
1
“/” indicates on/off page Flash access.
1
6
5
4+N
2
2
N is the number of read cycle clocks from external address valid till external data valid. In the case of zero wait states, N
= 2.
4+N
2
2
RCPU Instruction Fetches
2-1-1-1-1..
3
3
3
Assuming BBC is parked on the U-bus
2
—
1
4
4
SIUMCR[BURST_EN] = 1
2+N
2+N
—
1
5
5
Until address is valid on external pins
Peripheral Mode
(only external master is
active)
4/5
6
6
7
6
Slave Mode
(both external and
internal CPUs are active)
5/6
7
6
8
7
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...
