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CHAPTER 4 BUS INTERFACE
4.17.5 Read and Write Combination Cycles

This section provides a read and write combination cycle timing chart.

■Read and Write Combination Cycle Timing Chart
❍CS0 area: 16-bit bus width, word read
CS1 area: 8-bit bus width, half-word read
Figure 4.17-13 Example of Read and Write Combination Cycle Timing Chart
[Explanation of operation]
• The ab ove example shows the case, where an idle cycle (i dle bus cycle) is inserted in
between the chip select areas. When an idle cycle is inserted in between bus cycles, the
address of the previous bus cycle is output as is un til the nex t bus cycl e starts. B ecause of
this, CS0 to CS5X, which corresponds to the output address, are c ontinuously asserted.
• The abo ve example is a combination of 16-bit and 8-bit data bu ses.
As the maximum bus width is 16 bits, D23 to D16 and WR1X do not become I/O ports even
in the 8-bit access area (the CS1 area). D23 to D16 output indefinite data, and WR 1X is
negated.
BA1
CLK
A24-00 #0 #2 #0 #1
D31-24 #0 #2 #0 #1
D23-16 #1 #3
RDX
WR0X
WR1X
CS0X
CS1X
Word read cycle Half-word write cycle
CS0 area CS1 area
BA2 BA1 BA1 BA1
BA2 BA2 BA
Idle Idle