X28HC64
DATA
POLLING I/O
7
Figure 2.
DATA
Polling Bus Sequence
LAST
WRITE
WE
CE
OE
VIH
I/O7
HIGH Z
VOL
An
An
An
An
An
An
An
3857 FHD F12
VOH
X28HC64
READY
A0–A12
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
WRITES
COMPLETE?
YES
SAVE LAST DATA
AND ADDRESS
NO
READ LAST
ADDRESS
IO7
COMPARE?
YES
NO
READY
3857 FHD F13
4