STK14EC8 datasheet(12/19 Pages) SIMTEK

12 / 19 page

Simtek Confidential

Jan, 2008

Document Control #ML0060 Rev 1.1

STK14EC8

Preliminary

To reduce unneeded nonvolatile stores, AutoStore

and Hardware Store operations will be ignored

unless at least one WRITE operation has taken

place since the most recent STORE or RECALL

cycle. Software initiated STORE cycles are per-

formed regardless of whether a WRITE operation

has taken place. The HSB signal can be monitored

by the system to detect an AutoStore cycle is in

progress.

HARDWARE STORE (HSB) OPERATION

The STK14EC8 provides the HSB pin for controlling

and acknowledging the STORE operations. The

HSB pin can be used to request a hardware STORE

cycle. When the HSB pin is driven low, the

STK14EC8 will conditionally initiate a STORE oper-

ation after tDELAY. An actual STORE cycle will only

begin if a WRITE to the SRAM took place since the

last STORE or RECALL cycle. The HSB pin has a

very resistive pullup and is internally driven low to

indicate a busy condition while the STORE (initiated

by any means) is in progress. This pin should be

externally pulled up if it is used to drive other inputs.

SRAM READ and WRITE operations that are in

progress when HSB is driven low or when VCC falls

below Vswitch are given time to complete before the

STORE operation is initiated. After AUTOSTORE or

HSB goes low, the STK14EC8 will continue to allow

SRAM operations for tDELAY. During tDELAY, multiple

SRAM READ operations may take place. If a WRITE

is in progress when HSB is pulled low, it will be

allowed a time, tDELAY, to complete. However, any

SRAM WRITE cycles requested after HSB goes low

will be inhibited until HSB returns high.

If HSB is not used, it should be left unconnected.

HARDWARE RECALL (POWER-UP)

During power up or after any low-power condition

(VCC<VSWITCH), an internal RECALL request will be

latched. When VCC once again exceeds the sense

voltage of VSWITCH, a RECALL cycle will automati-

cally be initiated and will take tHRECALL to complete.

SOFTWARE STORE

Data can be transferred from the SRAM to the non-

volatile memory by a software address sequence.

The STK14EC8 software STORE cycle is initiated

by executing sequential E controlled or G controlled

READ cycles from six specific address locations in

exact order. During the STORE cycle, previous data

is erased and then the new data is programmed into

the nonvolatile elements. Once a STORE cycle is

initiated, further memory inputs and outputs are dis-

abled until the cycle is completed.

To initiate the software STORE cycle, the following

READ sequence must be performed:

Once the sixth address in the sequence has been

entered, the STORE cycle will commence and the

chip will be disabled. It is important that READ

cycles and not WRITE cycles be used in the

sequence and that G is active. After the tSTORE cycle

time has been fulfilled, the SRAM will again be acti-

vated for READ and WRITE operation.

SOFTWARE RECALL

Data can be transferred from the nonvolatile mem-

ory 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 soft-

ware STORE initiation. To initiate the RECALL cycle,

the following sequence of E controlled or G con-

trolled READ operations must be performed:

Internally, RECALL is a two-step procedure. First,

the SRAM data is cleared, and second, the nonvola-

tile information is transferred into the SRAM cells.

After the tRECALL cycle time, the SRAM will once

again be ready for READ or WRITE operations. The

RECALL operation in no way alters the data in the

nonvolatile storage elements. Care must be taken

so the controlling falling edge is glitch and ring free

so as not to double clock the read address.

1 Read Address

0x4E38

Valid READ

2 Read Address

0xB1C7 Valid READ

3 Read Address

0x83E0

Valid READ

4 Read Address

0x7C1F

Valid READ

5 Read Address

0x703F

Valid READ

6 Read Address

0x8FC0

Initiate STORE Cycle

1 Read Address

0x4E38

Valid READ

2 Read Address

0xB1C7 Valid READ

3 Read Address

0x83E0

Valid READ

4 Read Address

0x7C1F

Valid READ

5 Read Address

0x703F

Valid READ

6 Read Address

0x4C63

Initiate RECALL Cycle

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