Information

Note
Throughout this section:
• FB_D[X] indicates a 32-, 16-, or 8-bit wide data bus
• FB_A[Y] indicates an address bus that can be 32, 24, or 16
bits wide.
29.4.11.1 Basic Read Bus Cycle
During a read cycle, the MCU receives data from memory or a peripheral device. The
following figure shows a read cycle flowchart.
1. Decode address.
3. Assert FB_TA (external termination).
1. Negate FB_TA (external termination).
1. Set FB_R/W to read.
2. Assert FB_CSn.
(auto-acknowledge/internal termination).
2. Sample FB_TA low and latch data.
1. Start next cycle.
System
2. Place address on the external address signals.
2. Drive data on the external data signals.
1. Select the appropriate slave device.
3. Assert transfer start.
1. Negate transfer start.
1. FlexBus asserts internal FB_TA
Microcontroller
Figure 29-25. Read Cycle Flowchart
The read cycle timing diagram is shown in the following figure.
Note
FB_TA does not have to be driven by the external device for
internally-terminated bus cycles.
Note
The processor drives the data lines during the first clock cycle
of the transfer with the full 32-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.
Functional description
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
660
Preliminary
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