Cypress STK11C68 User Manual

STK11C68

64 Kbit (8K x 8) SoftStore nvSRAM

Features

STORE/

RECALL

CONTROL

POWER

CONTROL

SOFTWARE

DETECT

STATIC RAM

ARRAY

128 X 512

Quantum Trap

128 X 512

STORE

RECALL

COLUMN I/O

COLUMN DEC

ROW DECODER

INPUT BUFFERS

OE

CE

WE

HSB

V

CC

V

CAP

A

0

-

A

12

A

0

A

1

A

2

A

3

A

4

A

10

A

5

A

6

A

7

A

8

A

9

A

11

A

12

DQ

0

DQ

1

DQ

2

DQ

3

DQ

4

DQ

5

DQ

6

DQ

7

Logic Block Diagram

■

25 ns, 35 ns, and 45 ns access times

■

Pin compatible with industry standard SRAMs

■

Software initiated nonvolatile STORE

■

Unlimited Read and Write endurance

■

Automatic RECALL to SRAM on power up

■

Unlimited RECALL cycles

■

1,000,000 STORE cycles

■

100 year data retention

■

Single 5V+10% operation

■

Commercial and industrial temperature

■

28-pin (330 mil) SOIC package

■

28-pin (300 mil) CDIP and 28-pad (350 mil) LCC packages

■

RoHS compliance

Functional Description

The Cypress STK11C68 is a 64Kb fast st atic RAM with a nonvol­atile element in each memory cell. The embedded nonvolatile
elements incorporate QuantumTrap technology producing the
world’s most reliable nonvolatile memory. The SRAM provides
unlimited read and write cycles, while independent n onvolatile
data resides in the highly reliable QuantumTrap cell. Data
transfers under software control from SRAM to the nonvolatile
elements (the STORE operation). On power up, data is automat­ically restored to the SRAM (the RECALL operation) from the
nonvolatile memory. RECALL operations are also available
under software control.

Cypress Semiconductor Corporation • 198 Champion Court • San Jose,CA 95134-1709 • 408-943-2600
Document Number: 001-50638 Rev. ** Revised January 30, 2009

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STK11C68

Pin Configurations

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Pin Definitions

Figure 1. Pin Diagram - 28-Pin SOIC/DIP and 28-Pin LLC

Pin Name Alt IO Type Description

A

0–A12

DQ

-DQ

0

7

WE

W

CE E

OE

V

SS

V

CC

Document Number: 001-50638 Rev. ** Page 2 of 16

G

Input Address Inputs. Used to select one of the 8,192 bytes of the nvSRAM.

Input or

Bidirectional Data IO Lines. Used as input or output lines depending on operation.

Output

Input Write Enable Input, Active LOW. When the chip is enabled and WE is LOW, data on the

IO pins is written to the specific address location.

Input Chip Enable Input, Active LOW. W hen LOW, selects th e chip. When H IGH, desel ects the

chip.

Input Output Enable, Active LOW. The active LOW OE input enables the data output buffers

during read cycles. Deasserting OE

HIGH causes the IO pins to tri-state.

Ground Ground for the Device. The device is connected to ground of the system.

Power Supply Power Supply Inputs to the Device.

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STK11C68

Device Operation

The STK11C68 is a versatile memory chip that provides several
modes of operation. The STK16C88 can operate as a standard
8K x 8 SRAM. A 8K x 8 array of nonvolatile storage ele ments
shadow the SRAM. SRAM data can be copied nonvolatile
memory or nonvolatile data can be recalled to the SRAM.

SRAM Read

The STK11C68 performs a Read cycle whenever CE and OE are
LOW while WE
determines the 8,192 data bytes accessed. When the Read is
initiated by an address transition, the outputs are valid after a
delay of t
the outputs are valid at t
cycle 2). The data outputs repeatedly respond to address
changes within the t
tions on any control input pins, and remains valid until a nother
address change or until CE
brought LOW.

is HIGH. The address specified on pins A

(Read cycle 1). If the Read is initiated by CE or OE,

AA

or at t

ACE

access time without the need for transi-

AA

, whichever is later (Read

DOE

or OE is brought HIGH, or WE

0–12

SRAM Write

A Write cycle is performed whenever CE and WE are LOW . Th e
address inputs must be stable prior to entering the Write cycle
and must remain stable until either CE
end of the cycle. The data on the common IO pins DQ
written into the memory if it has valid t
controlled Write or before the end of an CE controlled Write.
Keep OE

HIGH during the entire Write cycle to avoid data bus
contention on common IO lines. If OE
circuitry turns off the output buffers t

or WE goes HIGH at the

, before the end of a WE

SD

0–7

is left LOW, internal

after WE goes LOW.

HZWE

are

Software ST ORE

Data is transferred from the SRAM to the nonvolatile memory by
a software address sequence. The STK11C68 software ST ORE
cycle is initiated by executing sequential CE controlled Read
cycles from six specific address locations in exact order. During
the STORE cycle, an erase of the previous nonvolatile data is
first performed followed by a program of the nonvolatile
elements. When a STORE cycle is initiated, input and output are
disabled until the cycle is completed.

Because a sequence of Reads from specific addresses is used
for STORE initiation, it is important that no other Read or Write
accesses intervene in the sequence. If they intervene, the
sequence is aborted and no STORE or RECALL takes place.

To initiate the software STORE cycle, the following Read
sequence is performed:

1. Read address 0x0000, Valid READ

2. Read address 0x1555, Valid READ

3. Read address 0x0AAA, Valid READ

4. Read address 0x1FFF, Valid READ

5. Read address 0x10F0, Valid READ

6. Read address 0x0F0F, Initiate STORE cycle

The software sequence is clocked with CE
When the sixth address in the sequence is entered, the STORE
cycle commences and the chip is disabled. It is important that
Read cycles and not Write cycles are used in the sequence. It is

controlled Reads.

not necessary that OE

cycle time is fulfilled, the SRAM is again activated for

t

STORE

Read and Write operation.

is LOW for a valid sequence. After the

Software RECALL

Data is transferred from the nonvolatile memory to the SRAM by
a software address sequence. A software RECALL cycle is
initiated with a sequence of Read operations in a manner similar
to the software STORE initiation. To initiate the RECALL cycle,
the following sequence of CE

controlled Read operations is

performed:

1. Read address 0x0000, Valid READ

2. Read address 0x1555, Valid READ

3. Read address 0x0AAA, Valid READ

4. Read address 0x1FFF, Valid READ

5. Read address 0x10F0, Valid READ

6. Read address 0x0F0E, Initiate RECALL cycle

Internally, RECALL is a two step procedure. First, the SRAM data
is cleared; then, the nonvolatile information is transferred into the
SRAM cells. After the t
ready for Read and Write operations. The RECALL operation

cycle time, the SRAM is again

RECALL

does not alter the data in the nonvolatile elements. The nonvol­atile data can be recalled an unlimited number of times.

Hardware RECALL (Power Up)

During power up or after any low power condition (VCC <
V
once again exceeds the sense voltage of V
cycle is automatically initiated and takes t

), an internal RECALL request is latched. When V

RESET

SWITCH

HRECALL

, a RECALL

to complete.

CC

If the STK11C68 is in a Write state at the end of power up
RECALL, the SRAM

data is corrupted. To help avoid this
situation, a 10 Kohm resistor is connected either be tween WE
and system VCC or between CE and system VCC.

Hardware Protect

The STK11C68 offers hardware protection against inadvertent
STORE operation and SRAM Writes during low voltage condi­tions. When V
operations and SRAM Writes are inhibited.

CAP<VSWITCH

, all externally initiated STORE

Noise Considerations

The STK11C68 is a high speed memory. It must have a high
frequency bypass capacitor of approximately 0.1 µF connected
between V
as possible. As with all high speed CMOS ICs, careful routing of

CC

and V

using leads and traces that are as short

SS,

power, ground, and signals reduce circuit noise.

Low Average Active Power

CMOS technology provides the STK11C68 the benefit of
drawing significantly less current when it is cycled at times longer
than 50 ns. Figure 2 shows the relationship between I
Read or Write cycle time. Worst case current consumption is
shown for both CMOS and TTL input levels (commercial temper­ature range, VCC = 5.5V, 100% duty cycle on chip enable). Only
standby current is drawn when the chip is disabled. The overall

CC

and

Document Number: 001-50638 Rev. ** Page 3 of 16

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STK11C68

average current drawn by the STK11C68 depends on the

Note

1. The six consecutive addresses must be in the order listed. WE

must be high during all six consecutive CE controlled cycles to enable a nonvolatile cycle.

following items:

■

The duty cycle of chip enable

■

The overall cycle rate for accesses

■

The ratio of Reads to Writes

■

CMOS versus TTL input levels

■

The operating temperature

■

The VCC level

■

IO loading

Figure 2. Current Versus Cycle Time (Read)

Figure 3. Current Versus Cycle Time (Write)

Best Practices

nvSRAM products have been used effectively for over 15 years.
While ease of use is one of the product’s main system values,
experience gained working with hundreds of applications has
resulted in the following suggestions as best practices:

■

The nonvolatile cells in an nvSRAM are programmed on the
test floor during final test and quality assurance. Incoming
inspection routines at customer or contract manufacturer’s
sites sometimes reprograms these values. Final NV patterns
are typically repeating patterns of AA, 55, 00, FF, A5, or 5A.
The end product’s firmware should not assume that an NV array
is in a set programmed state. Routines that check memory
content values to determine first time system configuration,

■

cold or warm boot status, and so on must always program a
unique NV pattern (for example, complex 4-byte pattern of 46
E6 49 53 hex or more random bytes) as part of the final system
manufacturing test to ensure these system routines work
consistently.

■

Power up boot firmware routines should rewrite the nvSRAM
into the desired state. While the nvSRAM is shipped in a preset
state, best practice is to again rewrite the nvSRAM into the
desired state as a safeguard against events that might flip the
bit inadvertently (program bugs, incoming inspection routines,
and so on).

Table 1. Hardware Mode Selection

CE WE A12–A0 Mode IO Notes

L H 0x0000

L H 0x0000

Document Number: 001-50638 Rev. ** Page 4 of 16

Read SRAM

0x1555

0x0AAA

0x1FFF
0x10F0
0x0F0F

Read SRAM
Read SRAM
Read SRAM
Read SRAM

Nonvolatile STORE

Read SRAM

0x1555

0x0AAA

0x1FFF
0x10F0
0x0F0E

Read SRAM
Read SRAM
Read SRAM
Read SRAM

Nonvolatile RECALL

Output Data
Output Data
Output Data
Output Data
Output Data

Output High Z

Output Data
Output Data
Output Data
Output Data
Output Data

Output High Z

[1]

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STK11C68

Maximum Ratings

Note

2. CE

> VIH does not produce standby current levels until any nonvolatile cycle in progress has timed out.

Exceeding maximum ratings may shorten the useful life of the
device. These user guidelines are not tested.

Storage Tem perature ................................. –65°C to +150°C

Temperature under bias..............................–55°C to +125°C

Supply Voltage on VCC Relative to GND..........–0.5V to 7.0V

Voltage on Input Relative to Vss............–0.6V to V

Voltage on DQ

...................................–0.5V to Vcc + 0.5V

0-7

+ 0.5V

CC

Power Dissipation .........................................................1.0W

DC Output Current (1 output at a time, 1s duration).... 15 mA

Operating Range

Range

Commercial 0°C to +70°C 4.5V to 5.5V
Industrial -40°C to +85°C 4.5V to 5.5V

Ambient

Temperature

V

CC

DC Electrical Characteristics

Over the operating range (VCC = 4.5V to 5.5V)

Parameter Description Test Conditions Min Max Unit

I

CC1

I

CC2

I

CC3

I

SB1

[2]

Average VCC Current tRC = 25 ns

t

= 35 ns

RC

t

= 45 ns

RC

Dependent on output loading and cycle rate.
Values obtained without output loads.
I

= 0 mA.

OUT

Average VCC Current
during STORE

Average VCC Current at

= 200 ns, 5V, 25°C

t

RC

Typical
VCC Standby Current

(Standby, Cycling TTL
Input Levels)

All Inputs Do Not Care, VCC = Max
Average current for duration t

WE

> (VCC – 0.2V). All other inputs cycling.
Dependent on output loading and cycle rate. Values obtained
without output loads.

tRC = 25 ns, CE > V
tRC = 35 ns, CE > V
tRC = 45 ns, CE > V

IH
IH
IH

Commercial 90

75
65

Industrial 90

75
65

3mA

STORE

10 mA

Commercial 27

23
20

Industrial 28

24
21

[2]

I

SB2

I

IX

I

OZ

V

V
V
V

IH

IL
OH
OL

VCC Standby Current CE > (VCC – 0.2V). All others V

– 0.2V). Standby current level after

(V

CC

nonvolatile cycle is complete.

< 0.2V or >

IN

Inputs are static. f = 0 MHz.

Input Leakage Current VCC = Max, VSS < V
Off State Output

VCC = Max, VSS < V

Leakage Current

< V

IN

CC

< VCC, CE or OE > V

IN

Input HIGH Voltage 2.2 VCC +

Input LOW Voltage VSS – 0.5 0.8 V
Output HIGH Voltage I
Output LOW Voltage I

= –4 mA 2.4 V

OUT

= 8 mA 0.4 V

OUT

Commercial 750 μA

Industrial 1500 μA

-1 +1 μA

or WE < V

IH

IL

-5 +5 μA

0.5

Data Retention and Endurance

Parameter Description Min Unit

DATA
NV

C

R

Data Retention 100 Years
Nonvolatile STORE Operations 1,000 K

mA
mA
mA

mA
mA
mA

mA
mA
mA

mA
mA
mA

V

Document Number: 001-50638 Rev. ** Page 5 of 16

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