X28C64
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
X28C64
READY
A –A
0
12
An
An
An
An
An
An
An
3853 FHD F12
Figure 3. DATA Polling Software Flow
DATA Polling can effectively halve the time for writing to
the X28C64. The timing diagram in Figure 2 illustrates
the sequence of events on the bus. The software flow
diagraminFigure3illustratesonemethodofimplement-
ing the routine.
WRITE DATA
NO
WRITES
COMPLETE?
YES
SAVE LAST DATA
AND ADDRESS
READ LAST
ADDRESS
IO
NO
7
COMPARE?
YES
X28C64
READY
3853 FHD F13
4