Data read mode, Data write mode – Rainbow Electronics DS1543 User Manual
Page 3
DS1543
3 of 17
DS1543 BLOCK DIAGRAM Figure 1
DS1543 OPERATING MODES Table 1
V
CC
CE
OE
WE
DQ0-DQ7
A0-A12
MODE
POWER
V
IH
X
X
HIGH-Z
X
DESELECT
STANDBY
V
IL
X
V
IL
D
IN
A
IN
WRITE
ACTIVE
V
IL
V
IL
V
IH
D
OUT
A
IN
READ
ACTIVE
In Tolerance
V
IL
V
IH
V
IH
HIGH-Z
A
IN
READ
ACTIVE
V
BAT
< V
CC
<
Tolerance
X
X
X
HIGH-Z
X
DESELECT
CMOS STANDBY
<V
BAT
X
X
X
HIGH-Z
X
DATA
RETENTION
BATTERY
CURRENT
DATA READ MODE
The DS1543 is in the read mode whenever
CE
(chip enable) is low and
WE
(write enable) is high. The
device architecture allows ripple through access to any valid address location. Valid data will be
available at the DQ pins within t
AA
after the last address input is stable, providing that
CE
and
OE
access
times are satisfied. If
CE
or
OE
access times are not met, valid data will be available at the latter of chip
enable access (t
CEA
) or at output enable access time (t
OEA
). The state of the data input/output pins (DQ) is
controlled by
CE
and
OE
. If the outputs are activated before t
AA
, the data lines are driven to an
intermediate state until t
AA
. If the address inputs are changed while
CE
and
OE
remain valid, output data
will remain valid for output data hold time (t
OH
) but will then go indeterminate until the next address
access.
DATA WRITE MODE
The DS1543 is in the write mode whenever
WE
and
CE
are in their active state. The start of a write is
referenced to the latter occurring transition of
WE
or
CE
. The addresses must be held valid throughout
the cycle.
CE
and
WE
must return inactive for a minimum of t
WR
prior to the initiation of a subsequent
read or write cycle. Data in must be valid t
DS
prior to the end of the write and remain valid for t
DH
afterward. In a typical application, the
OE
signal will be high during a write cycle. However,
OE
can be