Fujitsu FR81S User Manual
CHAPTER 36: EXTERNAL BUS INTERFACE
5. Operation
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : EXTERNAL BUS INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
41
5.9. RDY Pin Access Cycle Extension Function
This section shows the RDY pin access cycle extension function.
The read and write strobe cycles can be extended even after the auto wait cycles have finished by inputting
"0" to the RDY pin.
This function can be enabled by the RDY pin for access to the corresponding area when setting AWR:
RDYE to "1".
Use this function by setting the auto wait cycles of the corresponding area to 2 or more.
After the auto wait cycle has finished, the read and write strobe cycles are extended while "0" is input to
RDY. If "1" is input to RDY after this, the read or write strobe cycle finishes in the next cycle.
RDY Signal Input Specifications
The input RDY signal adheres to the following specifications.
·
Input RDY=1 except when extending the auto wait cycles.
·
Begin inputting RDY=0 after checking that access to an area covered by auto wait cycle extension has
started with ASX="L" and CSnX="L".
·
Start inputting RDY=0 before the auto wait cycle ends. It is prohibited to input RDY=0 after the auto
wait cycles have ended.
·
Input RDY=1 after the required extension cycles have finished.
Figure 5-8 RDY Timing Example
1 2 3 4 5 6 7 8 9
0
1
0
cycle n
o
.
SYSCLK
ASX
R
D
Y
RDX
WRnX
(n=0,1)
CSnX
(n=0,1,2,3)
CSnX
(n=0,1,2,3)
RDX
WRn
X
(n=0,1)
Auto wait cycle
Auto wait cycle
Basic example when
auto wait cycles
set to 2 cycles
Example of extending
wait cycles of basic
example by 3 cycles
using RDY
Extension cycles by RDY
MB91520 Series
MN705-00010-1v0-E
1240