Pressure sensors

Barometric pressure transmitters for SMT

ASB series

Preliminary data

AS SEN PD

2011-05-02

Please read Cautions and warnings and

Page 8 of 16

Important notes at the end of this document

.

I²C Status Bits

The sensor offers a full siute of diagnostic features to ensure robust system operation. The diagnostic states are indicated by

a transmission of the status of the 2 MSBs of the pressure high byte data.

Status Bits

Definition

00

Normal operation, good (fresh) data packet

01

Reserved

10

Stale data: Data that has already been fetched since the last measurement cycle

11

Internal error occured

I²C data fetch example

S

R

A

Start Condition

Device Slave Address (0x28h)

Read Bit

Acknowledge (ACK)

No Acknowledge (NACK)

Status Bit

Pressure Data

Temperature Data

x

reserved

N

S 0 1 0 1 0 0 0 1 A

S

0 0 0 0 0 1 1 0 A 0 1 1 0 0 1 1 0 A 0 1 0 1 1 0 0

A

1

Device Slave Address

0x28h

Pressure Data

00011001100110 = 0x666h = 1638d

0 mbar (rel.)

Temperature Data

01011001101 = 0x2CDh = 717d

20

°C

Status Bits

00

normal operation, fresh data package

S

R

A

Start Condition

Device Slave Address (0x28h)

Read Bit

Acknowledge (ACK)

No Acknowledge (NACK)

Status Bit

Pressure Data

Temperature Data

x

reserved

N

S 0 1 0 1 0 0 0 1 A

S

0 0 0 0 0 1 1 0 A 0 1 1 0 0 1 1 0 A 0 1 0 1 1 0 0

A

1

Device Slave Address

0x28h

Pressure Data

00011001100110 = 0x666h = 1638d

0 mbar (rel.)

Temperature Data

01011001101 = 0x2CDh = 717d

20

°C

Status Bits

00

normal operation, fresh data package

S 0 1 0 1 0 0 0 1 A

S

0 0 0 0 0 1 1 0 A 0 1 1 0 0 1 1 0 A 0 1 0 1 1 0 0

A

1

Device Slave Address

0x28h

Pressure Data

00011001100110 = 0x666h = 1638d

0 mbar (rel.)

Temperature Data

01011001101 = 0x2CDh = 717d

20

°C

Status Bits

00

normal operation, fresh data package

I²C protocol limitations

Please note:

•

Sending a start-stop condition without any transition on the CLK line (no clock pulses in between) creates a

communication error for the next communication, even if the next start condition is correct and the clock pulse is

applied. An additional start condition must be sent, which results in restoration of proper communication.

•

The restart condition – a falling SDA edge during data transmission when the CLK line is still high – creates the

same situation. The next communication fails, and an additional start condition must be sent for correct

communication.

•

A falling SDA edge is not allowed between the start condition and the first rising SCL edge. If using an I²C address

with the first bit 0, SDA must be held low from the start condition through the first bit.

•

If a data fetch is performed before or during the first measurement after power-on reset (POR), the fetched data is

invalid, even though the status bits report it as “valid” or “stale”.