m48t128y STMicroelectronics, m48t128y Datasheet - Page 6

• Manufacturer Part Number: m48t128y
• Description: 5.0 Or 3.3v, 1 Mbit 128 Kb X 8 Timekeeper Sram
• Manufacturer: STMicroelectronics

M48T128Y, M48T128V*
OPERATION MODES
Figure 4., page 5
ray and the quartz controlled clock oscillator. The
clock locations contain the year, month, date, day,
hour, minute, and second in 24 hour BCD format.
Corrections for 28, 29 (leap year - valid until 2100),
30, and 31 day months are made automatically.
Byte 1FFF8h is the clock control register. This byte
controls user access to the clock information and
also stores the clock calibration setting. The seven
clock bytes (1FFFFh - 1FFF8h) are not the actual
clock counters, they are memory locations consist-
ing of BiPORT™ READ/WRITE memory cells
within the static RAM array. The M48T128Y/V in-
cludes a clock control circuit which updates the
clock bytes with current information once per sec-
Table 2. Operating Modes
Note: X = V
6/22
Deselect
WRITE
READ
READ
Deselect
Deselect
Mode
1. See
IH
Table 11., page 18
or V
V
SO
IL
; V
4.5 to 5.5V
3.0 to 3.6V
to V
SO
illustrates the static memory ar-
V
V
= Battery Back-up Switchover Voltage.
PFD
or
SO
CC
(1)
(min)
for details.
(1)
V
V
V
V
E
X
X
IH
IL
IL
IL
V
V
G
X
X
X
X
IH
IL
ond. The information can be accessed by the user
in the same manner as any other location in the
static memory array. The M48T128Y/V also has its
own Power-Fail Detect circuit. This control circuitry
constantly monitors the supply voltage for an out
of tolerance condition. When V
ance, the circuit write protects the TIMEKEEPER
Register data and external SRAM, providing data
security in the midst of unpredictable system oper-
ation. As V
Switchover Voltage (V
tomatically switches to the battery, maintaining
data and clock operation until valid power is re-
stored.
V
V
V
W
X
X
X
IH
IH
IL
CC
DQ0-DQ7
High Z
High Z
High Z
High Z
D
D
OUT
falls below the Battery Back-up
IN
SO
), the control circuitry au-
Battery Back-up Mode
CMOS Standby
CC
Standby
Power
Active
Active
Active
is out of toler-
®