X5643, X5645 (Replaces X25643, X25645)

FN8135 Rev 1.00

Page 5 of 19

July 18, 2005

Figure 4. Sample VTRIP Reset Circuit

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 software protocol

allowing operation on a simple four-wire bus.

The device utilizes Intersil’s proprietary Direct Write™

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 syn-

chronous Serial Peripheral Interface (SPI) of many pop-

ular 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 out-

put 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 comple-

tion of a valid Write Cycle.

Status Register

The RDSR instruction provides access to the status register.

The status register may be read at any time, even during 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 nonvol-

atile 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

VTRIP

Adj.

Program

NC

NC

VP

Reset VTRIP

Test VTRIP

Set VTRIP

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