INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
FEATURES
•Real time clock keeps tracks of hundredths of
seconds, minutes, hours, days, date of the
months, and years.
•Watch function is transparent to RAM operation.
•Data Retention over 10 years in absence of power .
•512K x 8 NV SRAM directly replaces volatile static
RAM or EEPROM.
•Embedded lithium energy cell maintains calendar
operation and retains RAM data.
•Standard 32 pin DIP JEDEC Pinout.
•Month and year determine the number of days in
each month
•Full +10% operating range.
•Operating temperature range 0oC to 70oC.
•Available in 120 ns access time.
Functional Description
The IM 1251Y 4096K NV SRAM with Phantom
Clock is a fully static nonvolatile RAM organized as
512K words by 8 bits with a built-in real time clock.
This ‘NV SRAM’ has all the normal character-
istics of a CMOS static RAM with an important ben-
efit of data being retained in the absence of power.
Data retention current is so small that a miniature
lithium cell contained within the package provides an
energy source to preserve data. Protection against
data loss has also been incorporated to maintain data
integrity during power on/off conditions.
The Phantom Clock provides timekeeping information
including hundredths of seconds, seconds, minutes,
hours, day, date, month and year information. The date
at the end of the month is automatically adjusted for
months with less than 31 days, including correction for
leap years. The Phantom Clock operates in either 24-
hour or 12-hour format with an AM/PM indicator.
132
231
330
429
528
627
726
825
924
10 23
11 22
12 21
13 20
14 19
15 18
16 17
Pin configuration
A18/RST VCC
A16 A15
A14 A17
A12 WE
A7 A13
A6 A8
A5 A9
A4 A11
A3 OE
A2 A10
A1 CE
A0 I/O7
I/O0 I/O6
I/O1 I/O5
I/O2 I/O4
Gnd I/O3
PIN NAMES
A0-A18 Address Inputs
CE Chip Enable
GND Ground
I/O0-I/O-7 Input/Output
Vcc Power(+5V)
WE Write Enable
OE Output Enable
RST Reset
INNOVATIVE MICROTECHNOLOGY INC.Phone/Fax-440-322-8083.Website:www.innovativemicrotechnology.com
Parameter Symbol Min. Typ Max. Unit
Supply Voltage Vcc 4.5 5.0 5.5 V
Gnd 0 - 0 V
Input Voltage VIH 2.2 3.5 Vcc
+0.3 V
VIL 0 - 0.8 V
Recommended D.C. Operating Conditions
Maximum Ratings
Operating Temperature….0oC to 70oC
Storage Temperature…….0oC to 70oC
Soldering Temperature
And Time………………….260oC for 10 sec
Supply Voltage…………….-0.5V to 7.0V
Input Voltage………………-0.5V to 7.0V
Input/ Output Voltage…….-0.5V to
Vcc + 0.3V
Power Dissipation…………1.0W
WRITE MODE
The IM 1251Y is in the write mode whenever
CE and WE inputs are held low. The latter occurring
falling edge of either CE or WE determines the start of
a write cycle. A write is terminated by the earlier rising
edge of CE or WE. The address must be held valid
throughout the write cycle. WE must return to the high
state for a minimum recovery time (tWR) before another
Read or Write cycle can be initiated. CE or WE is high
during power on to perfect memory after Vcc reaches
Vcc (min) but before the processor stabilizes.
DATA RETENTION
The IM 1251Y provides full functional
capability for Vcc greater than 4.75V and write protects
at 4.5V. Data is retained in the absence of Vcc without
any additional support circuitry. The SRAM constantly
monitors Vcc. The moment Vcc decays, the RAM au-
tomatically write protects itself. All inputs to the RAM
become “don’t care” and all outputs are in high im-
pedance-state. As Vcc falls below approximately 3.0V
the power switching circuit connects the lithium energy
source to RAM to retain data. During power-on, when
Vcc rises above approximately 3.0V the power
switching circuit connects external Vcc to the RAM and
disconnects the lithium energy source. Normal RAM
operation can resume after Vcc becomes greater than
4.5V.
READ MODE
The IM 1251Y performs a read cycle whenever WE
high and CE low. The unique address specified by the
19 address inputs A0-A18 defines which of the
4,194,304 bytes of data is to be accessed. Valid data
will be available to the eight data output drivers within
access time tACC after the last address input is stable,
provided that CE and OE access times are satisfied. If
OE or CE access times are not satisfied, data access
will be measured from the limiting parameter (tCO or tOE),
rather than address. The state of the eight data I/O lines
is controlled by the OE and CE control signals. The
data lines may be in an indeterminate state between
tOH and tAA but the data lines will always have valid data
at tAA.
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
PHANTOM CLOCK REGISTER INFORMATION
The Phantom Clock information is contained
in 8 registers of 8 bits, each of which is sequentially
accessed one bit at a time after the 64-bit pattern rec-
ognition sequence has been completed. When updat-
ing the Phantom Clock registers, each register must
be handled in - groups of 8 bits. Writing and reading
individual bits within a register could produce errone-
ous results.
Data contained in the Phantom Clock register
is in binary coded decimal format (BCD). Reading and
writing the registers is always accomplished by step-
ping through all 8 registers, starting with bit 0 of regis-
ter 0 and ending with bit 7 of register 7.
PHANTOM CLOCK OPEARTION
Communication with the Phantom Clock is
established by pattern recognition on a serial bit stream
of 64 bits which must be matched by executing 64 con-
secutive write cycles containing the proper data on I/
O0. All access which occur prior to recognition of the
64-bit pattern are directed to memory.
After recognition is established, the next 64
read or write cycles either extract or update data in the
Phantom Clock, and memory access is inhibited.
Initially, a read cycle to any memory location
using the CE and OE control of the Phantom Clock
starts the pattern recognition sequence by moving a
pointer to the first bit of the 64-bit comparison register.
Next, 64 consecutive write cycles are executed using
the CE and WE control of the SmartWatch. These 64
write cycles are used only to gain access to the Phan-
tom Clock.
However , write cycle generated to gain access
to the Phantom Cycle are also writing data to a loca-
tion in the mated RAM. When the first write cycle is
executed it is compared to bit 0 of the 64-bit compari-
son register , If a match is found, the pointer increments
to the next location of the comparison register and
awaits the next write cycle. If a match is not found the
pointer does not advance and all subsequent write
cycles are ignored. If a read cycle occurs at any time
during pattern recognition, the present sequence is
aborted and the comparison register have been
matched. With a correct match for 64-bits the Phantom
Clock is enabled and data transfer to or from the time-
keeping register can proceed. The next 64-cycles will
cause the Phantom Clock to either receive or transmit
data on I/O0, depending the level of the OE pin or the
WE.
AM/PM 12/24 MODE
Bit 7of the hours register is defined as the 12-or-
24 hour mode selectbit. When high, the 12-hour mode
is selected. In the 12-hour mode, bit 5 is the AM/PM
bit with logic high being PM. In the 24-hour mode, bit 5
is the second 10-hour bit(20-23 hours).
AM/PM 12/24 MODE
Bit 7of the hours register is defined as the 12-or-
24 hour mode selectbit. When high, the 12-hour mode
is selected. In the 12-hour mode, bit 5 is the AM/PM
bit with logic high being PM. In the 24-hour mode, bit 5
is the second 10-hour bit(20-23 hours).
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
HEX
VALUE
1 1 0 0 0 1 0 1
0 0 1 1 1 0 1 0
1 0 1 0 0 0 1 1
0 1 0 1 1 1 0 0
1 1 0 0 0 1 0 1
0 0 1 1 1 0 1 0
1 1 0 0 0 1 0 1
0 1 0 1 1 1 0 0
PHANTOM CLOCK REGISTER DEFINTION
BYTE 0
BYTE 2
BYTE 3
BYTE 6
BYTE 5
BYTE 4
BYTE 7
BYTE 1
C5
3A
A3
5C
C5
3A
A3
5C
7 6 5 4 3 2 1 0
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
OSCILATTOR AND RESET BITS
Bits 4 and 5 of the day register are used to control the RESET and oscillator functions. Bit 4 controls
the RESET (pin 1). When the RESET bit is set to logic 1, the RESET input pin is ignored. When the RESET
bit is set to logic0, A low input on the RESET pin will cause the Phantom Clock to abort data transfer without
changing data in the watch registers. Bit 5 controls the oscillator. When set to logic 1, the oscillator is off.
When set to logic 0, the oscillator turns on and the watch becomes operational. These bits are shipped from
the factory set to a logic 1.
PHANTOM CLOCK REGISTER DEFINTION
0
1
2
3
4
5
6
7
REGISTER RANGE
(BCD)
00-99
00-59
00-59
01-12
00-23
01-07
01-13
01-12
00-99
0.1 SEC 0.01 SEC
10 SEC
0SECONDS
MINUTES
HOUR
DAY
DATE
MONTH
YEAR
10YEAR
0
0
00
0
0
0
0
0
10 DATE
10
MONTH
10 MIN
12/24 10 A/P HR
OSC RST
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
Notes 1. Typical values are measured at Ta = 25OC and Vcc = 5V
Capacitance
Parameter Description Test conditons Min. Typ Max Unit
CIInput capacitance Vi =0V - 5 10 pF
CI/O I/O capacitance VIO = 0V - 5 10 pF
DC ELECTRICAL CHARACTERISTICS (00C TO 700C; Vcc = 5V + 10%)
PARAMETER SYMBOL MIN TYP MAX UNITS
Input Leakage Current IIL -1.0 +1.0 A
I/O Leakage Current IIO -1.0 +1.0 A
CE > VIH < Vcc
Output Current @ 2.4V IOH -1.0 mA
Output Current @ 0.4V IOL 2.0 mA
Standby Current CE = 2.25V ICCS1 5.0 10 mA
Standby Current CE = Vcc- 0.5V ICCS2 3.0 5.0 mA
Operating Current tCYC = 120ns ICC01 85 mA
Notes 1. Typical values are measured at Ta = 25OC and Vcc = 5V
Capacitance
Parameter Description Test conditons Min. Typ Max Unit
CIInput capacitance Vi =0V - 5 10 pF
CI/O I/O capacitance VIO = 0V - 5 10 pF
DC ELECTRICAL CHARACTERISTICS (00C TO 700C; Vcc = 5V + 10%)
PARAMETER SYMBOL MIN TYP MAX UNITS
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
Switching Characteristics over the operating range
Parameter Description Min Max Unit
tRC Read cycle time 120 ns
tACC Address access time 120 ns
tOE Output enable access time 60 ns
tCO CE to output valid 120 ns
tCOE OE or CE to output valid 5 ns
tOD Output High Z from Deselection 40 ns
tOH Output hold from adds change 5 ns
tWC Write cycle time 120 ns
tAW Address setup time 0 ns
tWP Write pulse-width 90 ns
tWR Write recovery time 20 ns
tODW Output High Z from WE 40 ns
tOEW Output Active from WE 5 ns
tDS Input data setup time 50 ns
tDH Input data hold time 20 ns
PARAMETER SYMBOL MIN TYP MAX UNITS
CE at VIH before power-down tPD 0
u
s
Vcc Slow from 4.5 V to 0V tF 300 us
(CE at VIH)
Vcc Slow from 0V to 4.5 V tR 0 us
(CE at VIH)
CE at VIH after Power-Up tREC 2 ms
POWER DOWN/POWER UP TIMING
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
PARAMETER SYMBOL MIN TYP MAX UNITS
Read Cycle Time tRC 120 ns
CE Access Time tCO 100 ns
OE Access Time tOE 100 ns
CE to Output Low Z tCOE 10 ns
OE to Output Low Z tOEE 10 ns
CE to Output High Z tOD 40 ns
OE to Output High Z tODO 40 ns
Read Recovery tRR 20 ns
Write Cycle Time tWC 120 ns
Write Pulse Width tWP 100 ns
Write Recovery tWR 20 ns
Data Setup Time tDS 40 ns
Data Hold Time tDH 10 ns
CE Pulse Width tCW 100 ns
RESET Pulse Width tRST 200 ns
CE High to Power-Fail tPF 0 ns
PHANTOM CLOCK AC ELECTRICAL CHARACTERISTICS(00C TO 700C,Vcc= 4.5 TO 5.5V)
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
VIL
VIH VIH
VIH
VIL VIL
VIL VIL
tAW
tWP tWR
tODW tOEW
High
Impedance
DOUT
WRITE CYCLE 1
tDS tDH1
VIL
VIL
VIH
VIH Data In
Stable
DIN
CE
WE
VIH VIH
VIH VIL
VIH
VIH VIL
VIH
tCOE
tCOF
tOD
tOD
VOL
VOH
VOH
VOL
DOUT OUTPUT
DATA VALID
VIL VIL
CE
OE
READ CYCLE
ADDRESSES tRC
tACC
tCO
tOH
tWC
ADDRESSES VIL
VIH
RESET FOR PHATOM CLOCK
tRST
RST
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
VIH
VIL VIL
VIH
VIL VIL
tODW
tCOE
tDS tDH
VIL
VIL
VIH
VIH Data In
Stable
DIN
VIL VIL
VIH VIH
tAW tWP
tWR2
DOUT
WE
CE
ADDRESSES
WRITE CYCLE 2
tCOE
tCOE
tOEE
tOE
tCO
tODO
tRR
tOD
Output Data Valid
CE
OE
Q
Read cycle to Phantom Clock
tWC
VIH
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
tWR
tWP
tWC
tWR
tCW
tDH
tDH
tDS
Data IN Stable
D
CE
WE
OE=VIH
4.75V —————————————————————————————————————————————————
tF tR
3.2V ——————————————————————————————————————————————————
tPD tREC
LI Cell
Leakage Current Data Retention Time
tDR
Write Cycle to Phantom Clock
FIG. D POWER – DOWN/ POWER –ON CONDI-
TION
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
J
H
A
C
F
G E
D
DIM IN INCHES MIN. MAX.
A 1.52 1.54
B 0.695 0.72
C 0.395 0.415
D 0.1 0.13
E 0.015 0.021
F 0.12 0.16
G 0.09 0.11
H 0.59 0.63
J 0.008 0.012
B
INNOVATIVE
IM 1251
Serial RTC + SRAM
mm - yy
INNOVATIVE IM1251
4096K NV SRAM with Phantom Clock
