V53C8258H
MOSEL VITELIC
Data Output Operation
Table 1. V53C8258H Data Output
The V53C8258H Input/Output is controlled by
OE, CAS, WE and RAS. A RAS low transition
enables the transfer of data to and from the
selected row address in the Memory Array. A RAS
high transition disables data transfer and latches
the output data if the output is enabled. After a
memory cycle is initiated with a RAS low transition,
a CAS low transition or CAS low level enables the
internal I/O path. A CAS high transition or a CAS
high level disables the I/O path and the output driver
if it is enabled. A CAS low transition while RAS is
high has no effect on the I/O data path or on the
output drivers. The output drivers, when otherwise
enabled, can be disabled by holding OE high. The
OE signal has no effect on any data stored in the
output latches. A WE low level can also disable the
output drivers when CAS is low. During a Write
cycle, if WE goes low at a time in relationship to
CAS that would normally cause the outputs to be
active, it is necessary to use OE to disable the
output drivers prior to the WE low transition to allow
Data In Setup Time (tDS) to be satisfied.
Operation for Various Cycle Types
Cycle Type
I/O State
Read Cycles
Data from Addressed
Memory Cell
CAS-Controlled Write
Cycle (Early Write)
High-Z
WE-Controlled Write
Cycle (Late Write)
OE Controlled. High
OE = High-Z I/Os
Read-Modify-Write
Cycles
Data from Addressed
Memory Cell
EDO Read Cycle
Data from Addressed
Memory Cell
EDO Write Cycle
(Early Write)
High-Z
EDO Read-Modify-
Write Cycle
Data from Addressed
Memory Cell
RAS-only Refresh
High-Z
CAS-before-RAS
Refresh Cycle
Data remains as in
previous cycle
Power-On
CAS-only Cycles
High-Z
After application of the VCC supply, an initial
pause of 200 µs is required followed by a minimum
of 8 initialization cycles (any combination of cycles
containing a RAS clock). Eight initialization cycles
are required after extended periods of bias without
clocks (greater than the Refresh Interval).
During Power-On, the VCC current requirement of
the V53C8258H is dependent on the input levels of
RAS and CAS. If RAS is low during Power-On, the
device will go into an active cycle and ICC will exhibit
current transients. It is recommended that RAS and
CAS track with VCC or be held at a valid VIH during
Power-On to avoid current surges.
V53C8258H Rev. 1.4 February 1997
16
MOSEL [ MOSEL VITELIC, CORP ]
