STK17TA8-R35 datasheet(12/22 Pages) ETC

12 / 22 page

STK17TA8

February 2004

Document Control # ML0023 rev 0.3

information is transferred into the SRAM cells. After

the t

RECALL cycle time the SRAM will once again be

ready for READ and WRITE operations. The RECALL

operation in no way alters the data in the nonvolatile

elements.

PREVENTING STORES

The AutoStore™ function can be disabled by initiat-

ing an AutoStore Inhibit sequence. A sequence of

read operations is performed in a manner similar to

the software STORE initiation. To initiate the

AutoStore Inihibit sequence, the following sequence

of E controlled read operations must be performed:

1. Read address

4E38 (hex)

Valid READ

2. Read address

B1C7 (hex)

Valid READ

3. Read address

83E0 (hex)

Valid READ

4. Read address

7C1F (hex)

Valid READ

5. Read address

703F (hex)

Valid READ

6. Read address

8B45 (hex)

AutoStore Inhibit

The AutoStore Inhibit can be disabled by initiating

an AutoStore Inhibit Off sequence. A sequence of

read operations is performed in a manner similar to

the software RECALL initiation. To initiate the

AutoStore Inhibit Off sequence, the following

sequence of E controlled read operations must be

performed:

1. Read address

4E38 (hex)

Valid READ

2. Read address

B1C7 (hex)

Valid READ

3. Read address

83E0 (hex)

Valid READ

4. Read address

7C1F (hex)

Valid READ

5. Read address

703F (hex)

Valid READ

6. Read address

4B46 (hex)

AutoStore Inhibit Off

The last AutoStore Inhibit state is stored in nonvola-

tile memory and is retained through power cycling.

NOISE CONSIDERATIONS

The STK17TA8 is a high-speed memory and so

must have a high-frequency bypass capacitor of

approximately 0.1

µF connected between V

CAP and

SS, using leads and traces that are as short as pos-

sible. As with all high-speed CMOS ICs, normal care-

ful routing of power, ground and signals will help

prevent noise problems.

HARDWARE WRITE PROTECT

The STK17TA8 offers hardware protection against

inadvertent STORE operation and SRAM WRITEs dur-

ing low-voltage conditions. When V

CCX < VSWITCH, all

externally initiated STORE operations and SRAM

WRITE

s will be inhibited.

LOW AVERAGE ACTIVE POWER

The STK17TA8 draws significantly less current

when it is cycled at times longer than 50ns. Figure 3

shows the relationship between I

CC and READ cycle

time. Worst-case current consumption is shown for

commercial temperature range, V

CC = 3.6V, and

100% duty cycle on chip enable. Figure 4 shows the

same relationship for WRITE cycles. If the chip

enable duty cycle is less than 100%, only standby

current is drawn when the chip is disabled. The

overall average current drawn by the STK17TA8

depends on the following items: 1) the duty cycle of

chip enable; 2) the overall cycle rate for accesses;

3) the ratio of READs to WRITEs; 4) the operating

temperature; 5) the Vcc level; and 6) I/O loading.

Figure 3: Icc (max) Reads

Figure 4: Icc (max) Writes

100

150

200

Cycle Time (ns)

100

150

200

Cycle Time (ns)

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