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CY14B256P
(Rev.:2013)

256-Kbit (32 K × 8) Serial (SPI) nvSRAM with Real Time Clock

Cypress Semiconductor 

CY14B256P

Status Register

The Status Register bits are listed in Table 2. The Status Register

consists of a Ready bit (RDY) and data protection bits BP1, BP0,

WEN, and WPEN. The RDY bit can be polled to check the

ready/busy status while a nvSRAM STORE or Software RECALL

cycle is in progress. The Status Register can be modified by

WRSR instruction and read by RDSR instruction. However, only

the WPEN, BP1, and BP0 bits of the Status Register can be

modified by using the WRSR instruction. The WRSR instruction

has no effect on WEN and RDY bits. The default value shipped

from the factory for WEN, BP0, BP1, bits 4–6 and WPEN bits is

‘0’.

Table 2. Status Register Format

Bit 7

WPEN (0)

Bit 6

X (0)

Bit 5

X (0)

Bit 4

X (0)

Bit 3

BP1 (0)

Bit 2

BP0 (0)

Bit 1

WEN (0)

Bit 0

RDY

Table 3. Status Register Bit Definition

Bit

Definition

Description

Bit 0 (RDY)

Ready

Read only bit indicates the ready status of device to perform a memory access. This bit is

set to ‘1’ by the device while a STORE or Software RECALL cycle is in progress.

Bit 1 (WEN)

Write enable

WEN indicates if the device is write enabled. This bit defaults to ‘0’ (disabled) on power-up.

WEN = '1' --> Write enabled

WEN = '0' --> Write disabled

Bit 2 (BP0)

Block protect bit ‘0’ Used for block protection. For details see Table 4 on page 11.

Bit 3 (BP1)

Block protect bit ‘1’ Used for block protection. For details see Table 4 on page 11.

Bit 4–6

Don’t care

Bits are writable and volatile. On power-up, bits are written with ‘0’.

Bit 7 (WPEN) Write protect enable bit Used for enabling the function of write protect pin (WP). For details see Table 5 on page 11.

Read Status Register (RDSR) Instruction

The Read Status Register (RDSR) instruction provides access

to the Status Register. This instruction is used to probe the write

enable status of the device or the Ready status of the device.

RDY bit is set by the device to ‘1’ whenever a STORE or Software

RECALL cycle is in progress. The block protection and WPEN

bits indicate the extent of protection employed.

This instruction is issued after the falling edge of CS using the

opcode for RDSR.

Write Status Register (WRSR) Instruction

The WRSR instruction enables the user to write to the Status

Register. However, this instruction cannot be used to modify bit

0 and bit 1 (RDY and WEN). The BP0 and BP1 bits can be used

to select one of four levels of block protection. Further, WPEN bit

must be set to ‘1’ to enable the use of Write Protect (WP) pin.

WRSR instruction is a write instruction and needs writes to be

enabled (WEN bit set to ‘1’) using the WREN instruction before

it is issued. The instruction is issued after the falling edge of CS

using the opcode for WRSR followed by eight bits of data to be

stored in the Status Register. Since only bits 2, 3, and 7 can be

modified by WRSR instruction, it is recommended to leave the

bits 4-6 as ‘0’ while writing to the Status Register.

Note In CY14B256P, the values written to Status Register are

saved to nonvolatile memory only after a STORE operation. If

AutoStore is disabled, any modifications to the Status Register

must be secured by performing a Software STORE operation.

Document Number: 001-53881 Rev. *J

Page 9 of 37

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