X28HC64
DATA POLLING I/O
7
Figure 2. DATA Polling Bus Sequence
LAST
WRITE
WE
CE
OE
V
IH
V
HIGH Z
OH
I/O
7
V
OL
X28HC64
READY
A –A
0
12
An
An
An
An
An
An
An
3857 FHD F12
Figure 3. DATA Polling Software Flow
DATA Polling can effectively reduce the time for writing
to the X28HC64. The timing diagram in Figure 2 illus-
trates the sequence of events on the bus. The software
flow diagram in Figure 3 illustrates one method of
implementing the routine.
WRITE DATA
NO
WRITES
COMPLETE?
YES
SAVE LAST DATA
AND ADDRESS
READ LAST
ADDRESS
IO
NO
7
COMPARE?
YES
READY
3857 FHD F13
4