34AA02_V01 datasheet(8/40 Pages) MICROCHIP

8 / 40 page

34AA02/34LC02

DS20002029G-page 8

 2007-2022 Microchip Technology Inc. and its subsidiaries

3.0

FUNCTIONAL DESCRIPTION

The 34XX02 has two Software Write-Protect features

that allow the user to protect half of the array from being

written (Addresses 00h-7Fh). One command, Software

Write-Protect (SWP) will prevent writes to half of the

array and is resettable by using the Clear Software

Write-Protect (CSWP) command. The other command

is Permanent Software Write-Protect (PSWP), which is

not resettable and will permanently lock half the array

from being written to. The device still has an external

pin (WP) that allows the user to protect the entire array

if so desired.

The 34XX02 supports a bidirectional two-wire bus and

data transmission protocol. A device that sends data

onto the bus is defined as a transmitter and a device

receiving data, as a receiver. The bus has to be con-

trolled by a host device, which generates the Serial

Clock (SCL), controls the bus access and generates

the Start and Stop conditions, while the 34XX02 works

as client. Both host and client can operate as transmit-

ter or receiver, but the host device determines which

mode is activated.

4.0

BUS CHARACTERISTICS

The following bus protocol has been defined:

• Data transfer may be initiated only when the bus

is not busy

• During data transfer, the data line must remain

stable whenever the clock line is high. Changes in

the data line while the clock line is high will be

interpreted as a Start or Stop condition

Accordingly, the following bus conditions have been

defined (Figure 4-1).

4.1

Bus Not Busy (A)

Both data and clock lines remain high.

4.2

Start Data Transfer (B)

A high-to-low transition of the SDA line while the clock

(SCL) is high determines a Start condition. All

commands must be preceded by a Start condition.

4.3

Stop Data Transfer (C)

A low-to-high transition of the SDA line while the clock

(SCL) is high determines a Stop condition. All

operations must be ended with a Stop condition.

4.4

Data Valid (D)

The state of the data line represents valid data when,

after a Start condition, the data line is stable for the

duration of the high period of the clock signal. The data

on the line must be changed during the low period of

clock signal. There is one clock pulse per bit of data.

Each data transfer is initiated with a Start condition and

terminated with a Stop condition. The number of data

bytes transferred between the Start and Stop condi-

tions is determined by the host device and is, theoreti-

cally, unlimited; although only the last 16 bytes will be

stored when doing a write operation. When an over-

write does occur, it will replace data in a First-In

First-Out (FIFO) principle.

4.5

Acknowledge

Each receiving device, when addressed, is obliged to

generate an Acknowledge after the reception of each

byte. Exceptions to this rule relating to software write

protection are described in Section 7.0 “Write Protec-

tion”. The host device must generate an extra clock

pulse which is associated with this Acknowledge bit.

The device that acknowledges has to pull down the

SDA line during the Acknowledge clock pulse in such a

way that the SDA line is stable-low during the high

period of the Acknowledge-related clock pulse.

Moreover, setup and hold times must be taken into

account. During reads, a host must signal an

end-of-data to the client by not generating an

Acknowledge bit on the last byte that has been clocked

out of the client. In this case, the client (34XX02) will

leave the data line high to enable the host to generate

the Stop condition.

FIGURE 4-1:

DATA TRANSFER SEQUENCE ON THE SERIAL BUS

Note:

The 34XX02 does not generate any

Acknowledge

bits

internal

programming cycle is in progress.

SCL

SDA

(A)

(B)

(D)

(A)

(C)

Start

Condition

Address or

Acknowledge

Valid

Data

Allowed

to Change

Stop

Condition

34AA02 Arkusz danych(PDF) 8 Page - Microchip Technology

34AA02 Arkusz danych(HTML) 8 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Arkusz danych Pobierz

Link URL