Board Mount Pressure Sensor

AMS 6915 SERIES

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Datasheet AMS 6915

– Rev. 2.0

8/13

The I²C communication phases are as follows:

Idle period (bus is free)

When the bus is free, both I²C-

bus lines (SDA and SCL) are pulled up to supply voltage level (“high level”).

Start S (start condition)

Prior to any data transfer on the bus a start condition has to be generated. The start condition is always sent

by the I²C-

master. The start condition is defined as a transition from “high level” to “low level” on the SDA line

while the SCL line is still on “high level”. The digital data readout from the AMS 6915 is always initiated by a

start condition.

Stop P (stop condition)

The stop condition is always generated by the I²C-master after a data transfer has been completed. The stop

condition is defined as a transition from “low level” to “high level” on the SDA line while the SCL line is still on

“high level”. The digital data readout from the AMS 6915 is always terminated by a stop condition.

Valid data

Data is transmitted in bytes (8 bits), starting with the most significant bit (MSB). One data bit is transmitted

with each clock pulse. The transmitted bits are only valid when, following a start condition, the level on the

SDA line is constant as long as

the SCL line is on “high level”. Changes to the SDA level must be made

while the SCL l

ine is on “low level”.

Acknowledge A

After a byte has been transmitted the respective receiver (master or slave) has to send an acknowledge

(additional acknowledge bit) confirming the correct receipt of the data. For this purpose the master generates

an extra acknowledge-related clock pulse. The receiver sends the acknowledge bit by pulling the SDA line

down to “low level” during the additional clock pulse.

Addressing / Slave address (I²C-address AMS 6915)

After the start condition the master sends an addressing byte (the first byte after the start condition) which

determines which slave is selected. The addressing byte contains the individual 7-bit slave address of the

selected slave (AMS 6915) and a data direction bit (R/ W ). A

“0” for the R/ W bit indicates a transmission

from master to slave (W: write; the master wishes to transmit data to the selected slave), a

“1” a data request

(R: read; the master requests data from the slave).

The pressure sensors in the AMS 6915 series have a factory-programmed 7-bit slave address of 0x28Hex

(0101000bin), which is stored in the sensor’s EEPROM.

On request each AMS 6915 can be ordered with an individual 7-bit slave address programmed at the factory.

Using AMS 6915

’s USB starter kit the customer can program the individual slave address himself.

In general 7-bit addressing allows 128 different addresses. If more than one AMS 6915 should be connected

to the same I²C-bus, each pressure sensor requires an individual slave address.