XM28C040

4

DATA POLLING I/O

7

Figure 2.

DATA Polling Bus Sequence

Figure 3.

DATA Polling Software Flow

DATA Polling can effectively halve the time for writing to

the XM28C040. 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.

3873 FHD F10

3873 FHD F11

CE

OE

WE

I/O7

READY

LAST

WRITE

HIGH Z

VOL

VIH

A0–A18

An

An

An

An

An

An

VOH

An

WRITE DATA

SAVE LAST DATA

AND ADDRESS

READ LAST

ADDRESS

IO7

COMPARE?

READY

NO

YES

WRITES

COMPLETE?

NO

YES