M48T59 ST Microelectronics, M48T59 Datasheet - Page 9

• Manufacturer Part Number: M48T59
• Description: 64 Kbit 8Kb x8 TIMEKEEPER SRAM
• Manufacturer: ST Microelectronics

WRITE MODE
The M48T59/59Y/59V is in the Write Mode when-
ever W and E are low. The start of a write is refer-
enced from the latter occurring falling edge of W or
E. A write is terminated by the earlier rising edge
of W or E. The addresses must be held valid
throughout the cycle. E or W must return high for
a minimum of t
from Write Enable prior to the initiation of another
read or write cycle. Data-in must be valid t
prior to the end of write and remain valid for t
afterward. G should be kept high during write cy-
cles to avoid bus contention; although, if the output
bus has been activated by a low on E and G a low
on W will disable the outputs t
Table 11. Register Map
Keys:
Address
1FFDh
1FFCh
1FFFh
1FFEh
1FFBh
1FFAh
1FF9h
1FF8h
1FF7h
1FF6h
1FF5h
1FF4h
1FF3h
1FF2h
1FF1h
1FF0h
S = SIGN Bit
FT = FREQUENCY TEST Bit
R = READ Bit
W = WRITE Bit
ST = STOP Bit
0 = Must be set to zero
Y = ’1’ or ’0’
Z = ’0’ and are Read only
AF = Alarm Flag
BL = Battery Low
RPT4
RPT3
RPT2
RPT1
WDS
WDF
AFE
D7
ST
W
Y
0
0
0
0
0
EHAX
BMB4
D6
AF
FT
from Chip Enable or t
R
Y
Y
Y
Y
0
0
0
Alarm 10 Seconds
10 Years
Alarm 10 Minutes
10 Seconds
10 Minutes
BMB3
ABE
Al. 10 Hours
D5
CB
Al. 10 Date
S
Y
Z
0
WLQZ
10 Hours
10 Date
BMB2
after W falls.
10 M
CEB
D4
BL
Y
Y
Data
BMB1
DVWH
WHDX
WHAX
D3
Y
Y
Z
0
Calibration
BMB0
Alarm Seconds
Alarm Minutes
Alarm Hours
D2
Alarm Date
Y
Y
Z
Seconds
DATA RETENTION MODE
With valid V
erates as a conventional BYTEWIDE static RAM.
Should the supply voltage decay, the RAM will au-
tomatically power-fail deselect, write protecting it-
self when V
(min) window. All outputs become high imped-
ance, and all inputs are treated as "don’t care."
Note: A power failure during a write cycle may cor-
rupt data at the currently addressed location, but
does not jeopardize the rest of the RAM’s content.
At voltages below V
sured the memory will be in a write protected state,
provided the V
M48T59/59Y/59V may respond to transient noise
spikes on V
Minutes
Month
Hours
Date
Year
RB1
Day
D1
WDS = Watchdog Steering Bit
BMB0-BMB4 = Watchdog Multiplier Bits
RB0-RB1 = Watchdog Resolution Bits
AFE = Alarm Flag Enable
ABE = Alarm in Battery Back-up Mode Enable
RPT1-RPT4 = Alarm Repeat Mode Bits
WDF = Watchdog Flag
CEB = Century Enable Bit
CB = Century Bit
Y
Y
Z
CC
CC
CC
RB0
D0
CC
that reach into the deselect window
Y
Y
Z
M48T59, M48T59Y, M48T59V
applied, the M48T59/59Y/59V op-
falls within the V
fall time is not less than t
PFD
Alarm Seconds
Alarm Minutes
Century/Day
Alarm Hours
Alarm Date
Watchdog
Interrupts
Seconds
Minutes
Unused
Control
(min), the user can be as-
Month
Flags
Date
Hour
Year
Function/Range
BCD Format
PFD
00-01/01-07
(max), V
00-99
01-12
01-31
00-23
00-59
00-59
01-31
00-23
00-59
00-59
F
. The
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PFD