M48T128 ST Microelectronics, M48T128 Datasheet - Page 8

• Manufacturer Part Number: M48T128
• Description: 3.3V-5V 1 Mbit 128Kb x8 TIMEKEEPER SRAM
• Manufacturer: ST Microelectronics

M48T128Y, M48T128V
Table 10. Write Mode AC Characteristics
(T
Note: 1. C
Setting the Clock
Bit D7 of the Control Register (1FFF8h) is the
WRITE bit. Setting the WRITE bit to a '1', like the
READ bit, halts updates to the TIMEKEEPER reg-
isters. The user can then load them with the cor-
rect day, date, and time data in 24 hour BCD
format (see Table 11). Resetting the WRITE bit to
a '0' then transfers the values of all time registers
1FFFFh-1FFF9h to the actual TIMEKEEPER
counters and allows normal operation to resume.
After the WRITE bit is reset, the next clock update
will occur one second later.
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t
t
WHQX
WLQZ
A
Symbol
t
t
t
t
t
t
t
t
t
t
t
t
t
WLWH
WHAX
WHDX
= 0 to 70 °C)
DVWH
AVWH
AVWL
EHAX
DVEH
EHDX
ELEH
AVEH
AVAV
AVEL
2. If E goes low simultaneously with W going low, the outputs remain in the high impedance state.
(1, 2)
(1, 2)
L
= 5pF.
Write Cycle Time
Address Valid to Write Enable Low
Address Valid to Chip Enable Low
Write Enable Pulse Width
Chip Enable Low to Chip Enable High
Write Enable High to Address Transition
Chip Enable High to Address Transition
Input Valid to Write Enable High
Input Valid to Chip Enable High
Write Enable High to Input Transition
Chip Enable High to Input Transition
Write Enable Low to Output Hi-Z
Address Valid to Write Enable High
Address Valid to Chip Enable High
Write Enable High to Output Transition
Parameter
Min
70
50
55
10
30
30
10
60
60
0
5
5
5
0
Stopping and Starting the Oscillator
The oscillator may be stopped at any time. If the
device is going to spend a significant amount of
time on the shelf, the oscillator can be turned off to
minimize current drain on the battery. The STOP
bit is located at Bit D7 within 1FFF9h. Setting it to
a '1' stops the oscillator. The M48T128Y/V is
shipped from STMicroelectronics with the STOP
bit set to a '1'. When reset to a '0', the M48T128Y/
V oscillator starts after one second.
M48T128Y
-70
Max
25
Min
85
60
65
15
35
35
15
70
70
0
0
5
5
5
M48T128V
-85
Max
30
Unit
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns