A42U2604 Series
Selection Guide
Symbol
t
RAC
t
AA
t
CAC
t
OEA
t
RC
t
PC
Description
Maximum
RAS
Access Time
Maximum Column Address Access Time
Maximum
CAS
Access Time
Maximum Output Enable (
OE
) Access Time
Minimum Read or Write Cycle Time
Minimum EDO Cycle Time
-50
50
22
13
13
84
20
-60
60
27
15
15
100
24
-80
80
37
20
20
132
32
Unit
ns
ns
ns
ns
ns
ns
Functional Description
The A42U2604 reads and writes data by multiplexing an
22-bit address into a 11-bit(2K) row and column address.
RAS
and
CAS
are used to strobe the row address and the
column address, respectively.
A Read cycle is performed by holding the
WE
signal high
during
RAS
/
CAS
operation. A Write cycle is executed by
holding the
WE
signal low during
RAS
/
CAS
operation;
the input data is latched by the falling edge of
WE
or
CAS
, whichever occurs later. The data inputs and outputs
are routed through 4 common I/O pins, with
RAS
,
CAS
,
WE
and
OE
controlling the in direction.
valid as long as
RAS
and
OE
are low, and
WE
is high;
this is the only characteristic which differentiates Extended
Data Out operation from a standard Read or Fast Page
Read.
A memory cycle is terminated by returning both
RAS
and
CAS
high. Memory cell data will retain its correct state by
maintaining power and accessing all 2048(2K)
combinations of the 11-bit(2K) row addresses, regardless
of sequence, at least once every 32ms through any
RAS
cycle (Read, Write) or
RAS
Refresh cycle (
RAS
-only,
CBR, or Hidden). The CBR Refresh cycle automatically
controls the row addresses by invoking the refresh counter
and controller.
EDO Page Mode operation all 2048(2K) columns within a
selected row to be randomly accessed at a high data rate.
A EDO Page Mode cycle is initiated with a row address
latched by
RAS
followed by a column address latched by
CAS
. While holding
RAS
low,
CAS
can be toggled to
strobe changing column addresses, thus achieving shorter
cycle times.
The A42U2604 offers an accelerated Fast Page Mode
cycle through a feature called Extended Data Out, which
keeps the output drivers on during the
CAS
precharge
time (t
cp
). Since data can be output after
CAS
goes high,
the user is not required to wait for valid data to appear
before starting the next access cycle. Data-out will remain
Power-On
The initial application of the VCC supply requires a 200 µs
wait followed by a minimum of any eight initialization cycles
containing a
RAS
clock. During Power-On, the VCC
current is dependent on the input levels of
RAS
and
CAS
.
It is recommended that
RAS
and
CAS
track with VCC or
be held at a valid V
IH
during Power-On to avoid current
surges.
PRELIMINARY
(June, 2002, Version 0.3)
2
AMIC Technology, Inc.
AMICC [ AMIC TECHNOLOGY ]
