CY14B104LA, CY14B104NA

Document #: 001-49918 Rev. *H

Page 6 of 24

SRAM write operations that are in progress when HSB is driven

the STORE operation is initiated. However, any SRAM write

cycles requested after HSB goes LOW are inhibited until HSB

returns HIGH. In case the write latch is not set, HSB is not driven

LOW by the CY14B104LA/CY14B104NA. But any SRAM read

and write cycles are inhibited until HSB is returned HIGH by MPU

or other external source.

During any STORE operation, regardless of how it is initiated,

the CY14B104LA/CY14B104NA continues to drive the HSB pin

LOW, releasing it only when the STORE is complete. Upon

completion of the STORE operation, the nvSRAM memory

Leave the HSB unconnected if it is not used.

Hardware RECALL (Power-Up)

During

power-up

or

after

any

low

power

condition

this time, the HSB pin is driven LOW by the HSB driver and all

reads and writes to nvSRAM are inhibited.

Software STORE

Data is transferred from the SRAM to the nonvolatile memory by

a software address sequence. The CY14B104LA/CY14B104NA

software STORE cycle is initiated by executing sequential CE or

OE 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. After a STORE cycle is initiated, further

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, or the sequence is aborted

and no STORE or RECALL takes place.

To initiate the software STORE cycle, the following read

sequence must be performed.

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

The software sequence may be clocked with CE controlled reads

or OE controlled reads, with WE kept HIGH for all the six READ

sequences. After the sixth address in the sequence is entered,

the STORE cycle commences and the chip is disabled. HSB is

activated again for the read and write operation.

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,

perform the following sequence of CE or OE controlled read

operations must be performed.

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

Internally, RECALL is a two step procedure. First, the SRAM data

is cleared; then, the nonvolatile information is transferred into the

ready for read and write operations. The RECALL operation

does not alter the data in the nonvolatile elements.

Table 2. Mode Selection

CE

WE

OE

BHE, BLE[9]

Mode

I/O

Power

H

X

X

X

X

Not selected

Output high-Z

Standby

L

H

L

L

X

Read SRAM

Output data

Active

L

L

X

L

X

Write SRAM

Input data

Active

L

H

L

X

0x4E38

0xB1C7

0x83E0

0x7C1F

0x703F

0x8B45

Read SRAM

Read SRAM

Read SRAM

Read SRAM

Read SRAM

AutoStore

Disable

Output data

Output data

Output data

Output data

Output data

Output data

Active[11]

Notes

9. BHE and BLE are applicable for x16 configuration only.

The remaining address lines are don’t care.

11. The six consecutive address locations must be in the order listed. WE must be HIGH during all six cycles to enable a nonvolatile cycle.

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