X2816C
DEVICE OPERATION
Read
Read operations are initiated by both
OE
and
CE
LOW
and
WE
HIGH. The read operation is terminated by
either
CE
or
OE
returning HIGH. This two line control
architecture eliminates bus contention in a system envi-
ronment. The data bus will be in a high impedance state
when either
OE
or
CE
is HIGH.
Write
Write operations are initiated when both
CE
and
WE
are
LOW and
OE
is HIGH. The X2816C supports both a
CE
and
WE
controlled write cycle. That is, the address is
latched by the falling edge of either
CE
or
WE,
whichever
occurs last. Similarly, the data is latched internally by the
rising edge of either
CE
or
WE,
whichever occurs first.
A byte write operation, once initiated, will automatically
continue to completion, typically within 5ms.
Page Write Operation
The page write feature of the X2816C allows the entire
memory to be typically written in 640ms. Page write
allows two to sixteen bytes of data to be consecutively
written to the X2816C prior to the commencement of the
internal programming cycle. Although the host system
may read data from any other device in the system to
transfer to the X2816C, the destination page address of
the X2816C should be the same on each subsequent
strobe of the
WE
and
CE
inputs. That is, A
4
through A
10
must be the same for each transfer of data to the
X2816C during a page write cycle.
The page write mode can be entered during any write
operation. Following the initial byte write cycle, the host
can write an additional one to fifteen bytes in the same
manner as the first byte was written. Each successive
byte load cycle, started by the
WE
HIGH to LOW
transition, must begin within 20µs of the falling edge of
the preceding
WE.
If a subsequent
WE
HIGH to LOW
transition is not detected within 20µs, the internal auto-
matic programming cycle will commence. There is no
page write window limitation. The page write window is
infinitely wide, so long as the host continues to access
the device within the byte load cycle time of 20µs.
DATA
Polling
The X2816C 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 X2816C,
eliminating additional interrupt inputs or external hard-
ware. During the internal programming cycle, any at-
tempt to read the last byte written will produce the
complement of that data on I/O
7
(i.e., write data = 0xxx
xxxx, read data = 1xxx xxxx). Once the programming
cycle is complete, I/O
7
will reflect true data.
WRITE PROTECTION
There are three features that protect the nonvolatile data
from inadvertent writes.
• Noise Protection—A
WE
pulse which is typically
less than 10ns will not initiate a write cycle.
• V
CC
Sense—All functions are inhibited when V
CC
is
≤3V,
typically.
• Write Inhibit—Holding either
OE
LOW,
WE
HIGH,
or
CE
HIGH during power-up and power-down, will
inhibit inadvertent writes. Write cycle timing specifi-
cations must be observed concurrently.
ENDURANCE
Xicor E
2
PROMs are designed and tested for applica-
tions requiring extended endurance.
3
XICOR [ XICOR INC. ]
