X28HC64 データシートの表示（PDF） - Renesas Electronics
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X28HC64 Datasheet PDF : 18 Pages
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X28HC64
DATA Polling (I/O7)
The X28HC64 features DATA Polling as a method to indicate to
the host system that the byte write or page write cycle has
completed. DATA Polling allows a simple bit test operation to
determine the status of the X28HC64, eliminating additional
interrupt inputs or external hardware. During the internal
programming cycle, any attempt to read the last byte written will
LAST
WE WRITE
produce the complement of that data on I/O7 (i.e., write data =
0xxx xxxx, read data = 1xxx xxxx). Once the programming cycle is
complete, I/O7 will reflect true data.
DATA Polling can effectively reduce the time for writing to the
X28HC64. The timing diagram in Figure 3 illustrates the
sequence of events on the bus. The software flow diagram in
Figure 4 illustrates one method of implementing the routine.
CE
OE
VIH
I/O7
A0–A12
An
HIGH Z
VOL
An
An
An
An
An
FIGURE 3. DATA POLLING BUS SEQUENCE
VOH
X28HC64
READY
An
FN8109 Rev 4.00
June 27, 2016
WRITE DATA
WRITES
NO
COMPLETE?
YES
SAVE LAST DATA
AND ADDRESS
READ LAST
ADDRESS
IO7
NO
COMPARE?
YES
READY
FIGURE 4. DATA POLLING SOFTWARE FLOW
Page 4 of 18
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