5

FN8135.1

July 18, 2005

SPI SERIAL MEMORY

The memory portion of the device is a CMOS serial

EEPROM array with Intersil’s block lock protection.

The array is internally organized as x 8. The device

features a Serial Peripheral Interface (SPI) and soft-

ware protocol allowing operation on a simple four-wire

bus.

cell, providing a minimum endurance of 100,000

cycles and a minimum data retention of 100 years.

The device is designed to interface directly with the

synchronous Serial Peripheral Interface (SPI) of many

popular microcontroller families. It contains an 8-bit

instruction register that is accessed via the SI input,

with data being clocked in on the rising edge of SCK.

CS must be LOW during the entire operation.

All instructions (Table 1), addresses and data are trans-

ferred MSB first. Data input on the SI line is latched on

the first rising edge of SCK after CS goes LOW. Data is

output on the SO line by the falling edge of SCK. SCK is

static, allowing the user to stop the clock and then start

it again to resume operations where left off.

Write Enable Latch

The device contains a write enable latch. This latch

must be SET before a write operation is initiated. The

WREN instruction will set the latch and the WRDI

instruction will reset the latch (Figure 3). This latch is

automatically reset upon a power-up condition and

after the completion of a valid Write Cycle.

Status Register

The RDSR instruction provides access to the status regis-

ter. The status register may be read at any time, even dur-

ing a write cycle. The status register is formatted as

follows:

The Write-In-Progress (WIP) bit is a volatile, read only

bit and indicates whether the device is busy with an

internal nonvolatile write operation. The WIP bit is read

using the RDSR instruction. When set to a “1”, a non-

volatile write operation is in progress. When set to a

“0”, no write is in progress.

Table 1. Instruction Set

Note:

*Instructions are shown MSB in leftmost position. Instructions are transferred MSB first.

X5643/45

1

2

3

4

8

7

6

5

Adj.

Program

NC

NC

NC

RESET

4.7K

4.7K

10K

10K

+

7

6

5

4

3

210

WPEN

FLB

WD1

WD0

BL1

BL0

WEL

WIP

Instruction Name

Instruction Format*

Operation

WREN

0000 0110

Set the write enable latch (enable write operations)

SFLB

0000 0000

Set flag bit

WRDI/RFLB

0000 0100

Reset the write enable latch/reset flag bit

RSDR

0000 0101

Read status register

WRSR

0000 0001

Write status register (watchdog, block lock, WPEN & flag bits)

READ

0000 0011

Read data from memory array beginning at selected address

WRITE

0000 0010

Write data to memory array beginning at selected address

X5643, X5645