DS1330Y/AB
READ MODE
The DS1330 devices execut e a read cycle whenever
(Write Enable) is inact ive (high) and
(Chip
Ena ble ) and
(Output Enable) are active (low). The unique address specified by the 15 address inputs
(A0 – A14) defines w hich o f the 32,768 bytes o f dat a is to be acces sed. Valid data will be available t o the
e ig ht dat a out put dr ivers w it hin t ACC (Access T ime) after the last address input sig nal is stable, providing
that
and
(Output Enable) access times are also satisfied. If
and
access times are not
satisfied, t hen dat a acc ess must be me asured fro m t he later occu rring s ig na l (
or
) a nd t he l imitin g
parameter is either tCO for
or tOE for
rather than address access.
WRITE MODE
The DS1330 devices e xecu te a wr ite c ycle wh enever t he
and
sig na ls are in the act ive (lo w) st at e
after address inputs are stable. The later-occurring falling edge of
or
will determine the start of
the write c ycle. The wr it e cycle is terminated by the earlier rising edge of
or
. All address inputs
must be k ept va lid t hro ug hout t he wr it e c ycle.
must r et urn t o t he hig h st at e fo r a min i mum reco ve r y
time (tWR) before another cycle can be initiated. The
control signal should be kept inactive (high)
during write cycles to avoid bus contention. However, if the output drivers are enabled (
and
active ) then
will disable the outputs in tODW from its falling edge.
DATA RETENTION MODE
The DS1330AB provides full-functional capability for VCC greater than 4.75V and write protects by
4.5V. The DS1330Y provides full-functional capability for VCC greater than 4.5V and write protects by
4.25V. Data is maintained in the absence of VCC without any additional support circuitry. The NV
SRAMs constantly monitor VCC. Should the supply voltage decay, the NV SRAMs automatically write
prot ect the mse lves, a ll input s beco me “do n’t car e,” and a ll out puts beco me h ig h-imped ance. As VCC falls
below approximately 2.7V, the power switching circuit connects the lithium energy source to RAM to
retain data. During power-up, when VCC rises above approximately 2.7V, the power switching circuit
connects external VCC to the RAM and disconnects the lithium energy source. Normal RAM operation
can resume after VCC exceeds 4.75V for the DS1330AB and 4.5V for the DS1330Y.
SYSTEM POWER MONITORING
DS1330 devices have the ability to monitor the external VCC power supply. When an out-of-tolerance
power supply condit io n is detected, the NV SRAMs war n a pro cessor-based system of impending po wer
failure by asserting
. On power-up,
is held active for 200ms nominal to prevent system
oper ation dur ing power-on transients a nd to a llow tREC to elapse.
has an open drain o utput driver.
BATTERY MONITORING
The DS1330 devices automatically perform periodic battery voltage monitoring on a 24-hour time
interval. Such monitoring begins within tREC after VCC rises above VTP and is suspended when power
failure occurs.
After each 24-hour period has elapsed, the battery is connected to an internal 1MΩ test resistor for one
second. During this one second, if battery voltage falls below the battery voltage trip point (2.6V), the
batt ery war ning o utput
is asserted. Once asserted,
re mains act ive u ntil t he modu le is replaced.
The batter y is still retested after each VCC power-up , howe ver, even if
is act ive. If the bat tery vo ltage
is found to be higher than 2.6V during such testing,
is de-asserted and regular 24-hour testing
resumes.
has an open drain output driver.