All Sensors

DS-0350 Rev A

I2C Interface (Cont’d)

Figure 3 - I2C Communication Diagram

Page 7

I2C Bus Communications Overview

The I2C interface uses a set of signal sequences for communication. The following is a description of the sup-

ported sequences and their associated mnemonics. Refer to Figure 3 for the associated usage of the following

signal sequences.

Bus not Busy (I): During idle periods both data line (SDA) and clock line (SCL) remain HIGH.

START condition (ST): A HIGH to LOW transition of SDA line while the clock (SCL) is HIGH is interpreted as

START condition. START conditions are always set by the master. Each initial request for a pressure value has to

begin with a START condition.

Slave address (An): The I²C-bus requires a unique address for each device. The DLH sensor has a preconfigured

slave address (see specification table on Page 3). After setting a START condition the master sends the address

byte containing the 7 bit sensor address followed by a data direction bit (R/W). A “0” indicates a transmission

from master to slave (WRITE), a “1” indicates a device-to master request (READ).

Acknowledge (A or N): Data is transferred in units of 8 bits (1 byte) at a time, MSB first. Each data-receiving

device, whether master or slave, is required to pull the data line LOW to acknowledge receipt of the data. The

Master must generate an extra clock pulse for this purpose. If the receiver does not pull the data line down, a

NACK condition exists, and the slave transmitter becomes inactive. The master determines whether to send

the last command again or to set the STOP condition, ending the transfer.

DATA valid (Dn): State of data line represents valid data when, after a START condition, data line is stable for

duration of HIGH period of clock signal. Data on line must be changed during LOW period of clock signal.

There is one clock pulse per data bit.

STOP condition (P): LOW to HIGH transition of the SDA line while clock (SCL) is HIGH indicates a STOP con-

dition. STOP conditions are always generated by the master.

1.

Measurement Commands:Start-Single (tostart readingofsinglesample):

Start-Single

C23…C16: 0xAA

Start-Average2

C23…C16:0xAC

Start-Average4

C23…C16:0xAD

Start-Average8

C23…C16:0xAE

Start-Average16

C23…C16:0xAF

0x00

0x00

Setbybus master:I ST A6 A5 A4 A3 A2 A1 A0 W

C23 … C16

C15… C8

C7 …C0

SP I

Setby sensor:

AA

AN

2.

Status Read :

Setbybus master:I ST A6 A5 A4 A3 A2 A1 A0 RN SP I

Setby sensor:

A S7 …S0

3.

Data Read:

Setbybus master:I ST A6 A5 A4 A3 A2 A1 A0 RA

AA

AA

AN SP I

Setby sensor:

A S7 …S0

P23 … P16

P15… P8

P7 …P0

T23 … T16

T15 … T8

T7 … T0

Busstates:

Sensor Address:

Databits:

Idle:I

A6 …A0

Status:

S7 …S0

Start:

ST

Default: 0x29Pressure data:

P23… P0

Stop:SPTemperature data:

T23… T0

Ack:

ACommand Bits:

Nack:N

C23

… C0

“Read” bit (1): R

“Write”bit (0):W