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MCF5253 Reference Manual, Rev. 1
Freescale Semiconductor
8-1
Chapter 8
Bus Operation
This chapter describes bus functionality, the bus control signals, and the bus cycles provided for
data-transfer operations. Bus operation is defined for transfers initiated by the MCF5253 as a bus master
and for transfers initiated by an alternate bus master. This chapter includes descriptions of the error
conditions, bus arbitration, and the reset operation.
8.1
Bus Features
The MCF5253 bus operates using the following features:
•
24 bit address bus (24-bit for SDRAM access only 23-bit otherwise)
•
16 bit data bus
•
16 bit port size
•
Generates byte, word, longword, and line size transfers
•
Burst and burst-inhibited transfer support
•
Internal termination generation (TA)
8.2
Bus and Control Signals
Although the timing of these signals is referenced to the BCLK, it is not considered a bus signal. It is
expected that the clock will be routed as needed to meet application requirements.
summarizes
the MCF5253 bus signals. A brief description of the function of each signal follows.
NOTE
An overbar indicates an active-low signal.
Table 8-1. MCF5253 Bus Signal Summary
Signal Name
Direction
Description
A[24:1]
Out
Address bus
RW
Out
Read-write control
D[31:16]
In/Out
Data bus
CS0/CS4
Out
Chip select 0 / Chip select 4
CS1/QSPI_CS3/GPIO28
Out
Chip select 1
OE
Out
Output enable
Содержание MCF5253
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