16Mb: 1 MEG x16
EDO DRAM
GENERAL DESCRIPTION (continued)
of the two signals results in a BYTE WRITE cycle. CASL#
transitioning LOW selects an access cycle for the lower
byte (DQ0-DQ7), and CASH# transitioning LOW se-
lects an access cycle for the upper byte (DQ8-DQ15).
Each bit is uniquely addressed through the 20 ad-
dress bits during READ or WRITE cycles. These are
entered 10 bits (A0-A9) at a time. RAS# is used to latch
the first 10 bits and CAS#, the latter 10 bits. The CAS#
function also determines whether the cycle will be a
refresh cycle (RAS# ONLY) or an active cycle (READ,
WRITE or READ-WRITE) once RAS# goes LOW.
The CASL# and CASH# inputs internally generate a
CAS# signal that functions like the single CAS# input
on other DRAMs. The key difference is each CAS# input
(CASL# and CASH#) controls its corresponding eight
DQ inputs during WRITE accesses. CASL# controls
DQ0-DQ7, and CASH# controls DQ8-DQ15. The two
CAS# controls give the 1 Meg x 16 both BYTE READ and
BYTE WRITE cycle capabilities.
A logic HIGH on WE# dictates read mode, while a
logic LOW on WE# dictates write mode. During a WRITE
cycle, data-in (D) is latched by the falling edge of WE or
CAS# (CASL# or CASH#), whichever occurs last. An
EARLY WRITE occurs when WE is taken LOW prior to
either CAS# falling. A LATE WRITE or READ-MODIFY-
WRITE occurs when WE falls after CAS# (CASL# or
CASH#) was taken LOW. During EARLY WRITE cycles,
the data outputs (Q) will remain High-Z, regardless of
the state of OE#. During LATE WRITE or READ-
MODIFY-WRITE cycles, OE# must be taken HIGH to
disable the data outputs prior to applying input data.
If a LATE WRITE or READ-MODIFY-WRITE is attempted
while keeping OE# LOW, no WRITE will occur, and the
data outputs will drive read data from the accessed
location.
The 16 data inputs and 16 data outputs are routed
through 16 pins using common I/O. Pin direction is
controlled by OE# and WE#.
The 1 Meg x 16 DRAM must be refreshed periodi-
cally in order to retain stored data.
RAS#
V IH
V IL
CASL#/CASH#
V IH
V IL
ADDR
V IH
V IL
ROW
COLUMN (A)
COLUMN (B)
COLUMN (C)
COLUMN (D)
DQ V IOH
V IOL
OPEN
VALID DATA (A)
tOD
tOES
VALID DATA (A)
VALID DATA (B)
tOD
tOEHC
VALID DATA (C)
tOD
VALID DATA (D)
OE#
V IH
V IL
tOE
tOEP
The DQs go back to
Low-Z if
t
OES is met.
The DQs remain High-Z
until the next CAS# cycle
if
t
OEHC is met.
The DQs remain High-Z
until the next CAS# cycle
if
t
OEP is met.
DON’T CARE
UNDEFINED
Figure 1
OE# Control of DQs
1 Meg x 16 EDO DRAM
D52_B.p65 – Rev. B; Pub. 3/01
2
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2001, Micron Technology, Inc
MICRON [ MICRON TECHNOLOGY ]
