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CHAPTER 4 BUS INTERFACE
4.17.7 External Wait Cycles

This section provides an external wait cycle timing chart.

External Wait Cycle Timing Chart
Bus width: 16 bits, access: half-words
Figure 4.17-15 Example of External Wait Cycle Timing Chart
[Explanation of operation]
When i mplementing external wait c ycles, set the RDYE b it of EPCR0 to "1" to v alidate the
input of the external RDY pin.
When us ing the extern al RDY signa l, set at lea st 1 clock of au tomatic wait c ycle; that is , set
"001" or more in the WTC bit of the AMD. The RDY signa l is detected after, not during,
automatic wait cycles.
Enter the RD Y signal synchronously with the falling edge of the CLK pi n output. If the
external RDY is "L" at the falling edge of the CLK, a wait cycle is entered and the same BA1
cycle is repeated. If the external RDY is "H", the end of t he wait cycle is a ssumed and the
BA2 cycle is entered.
BA1 BA1 BA1 BA1 BA1 BA2
CLK
A24-00 #0 #0:1
D31-16
RDX
D31-16 #0,1
WR0X,1X wait wait wait RDY
RDY
Automatic Wait by RDY
Bus cycle
Read
Write
wait