Mini-FlexBus
11-11
Freescale Semiconductor
MCF51CN128 Reference Manual, Rev. 6
NOTE
Throughout this chapter FB_AD[
X
:0] indicates a 16-, or 8-bit wide data bus.
FB_AD[
] is an address bus that can be
-bits in width.
Figure 11-6. Read Cycle Flowchart
The read cycle timing diagram is shown in
NOTE
The processor drives the data lines during the first clock cycle of the transfer
with the full 20-bit address. This may be ignored by standard connected
devices using non-multiplexed address and data buses. However, some
applications may find this feature beneficial.
19:
X+1
12-, or 4
1. Select the appropriate slave device.
1. Decode address.
1. Set FB_R/W to read.
Assert FB_CS
n
.
2.
1. Mini-FlexBus asserts internal transfer
1. Start next cycle.
ColdFire device
System
2. Place address on FB_AD[19:0].
2. Drive data on FB_AD[
X
:0].
3. Assert FB_ALE.
1. Negate FB_ALE.
acknowledge (auto-acknowledge).