M48T559 ST Microelectronics, M48T559 Datasheet - Page 3

• Manufacturer Part Number: M48T559
• Description: 64 Kbit 8Kb x8 TIMEKEEPER SRAM with ADDRESS/DATA MULTIPLEXED
• Manufacturer: ST Microelectronics

Figure 3. Block Diagram
Table 3. Operating Modes
Note: 1. X = V
mation once per second. The information can be
accessed by the user in the same manner as any
other location in the static memory array.
The M48T559Y also has its own Power-fail Detect
circuit. The control circuitry constantly monitors
the single 5V supply for an out of tolerance condi-
tion.
Deselect
Write
Read
Read
Deselect
Deselect
Mode
2. See Table 7 for details.
3. AD0-AD7, AS0, AS1 active when E is high and V
32,768 Hz
CRYSTAL
LITHIUM
CELL
IH
or V
IL
V
; V
SO
SO
4.5V to 5.5V
to V
= Battery Back-up Switchover Voltage.
V CC
V
PFD
V
CC
OSCILLATOR AND
VOLTAGE SENSE
SO
RSTIN1
CLOCK CHAIN
(1)
(min)
SWITCHING
CIRCUITRY
IRQ/FT
AND
RSTIN2
(2)
POWER
RST
V
V
V
V
CC
E
X
X
V PFD
IH
IL
IL
IL
> V
PFD
.
V SS
16 x 8 BiPORT
SRAM ARRAY
SRAM ARRAY
V
V
V
R
X
X
X
IH
IH
IL
When V
tects the SRAM, providing a high degree of data
security in the midst of unpredictable system oper-
ation brought on by low V
approximately 3V, the control circuitry connects
the battery which maintains data and clock opera-
tion until valid power returns.
8176 x 8
E
CC
V
V
V
W
X
X
X
IH
IH
IL
is out of tolerance, the circuit write pro-
AD0-AD7
High Z
High Z
High Z
High Z
D
TRANSCEIVER
D
OUT
ADDRESS
IN
ADDRESS
LOWER
LATCH
UPPER
LATCH
DATA
CC
Battery Back-up Mode
. As V
CMOS Standby
Standby
AD0-AD7
Power
Active
Active
Active
CC
M48T559Y
AI01676B
falls below
(3)
W
R
AS1
AS0
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