11
2 I²C - communication
2.6
WRITE Operation
An I²C WRITE operation is initiated by the master sending the slave an address byte including a data
direction bit set to ‘0’ (WRITE). The address byte is followed by a command byte, and for applicable com-
mands two additional data bytes (optional). The digital pressure measuring cell’s internal micro-controller
evaluates the received command and processes the related routine. In the following a WRITE command
with two data bytes and another WRITE command without data bytes is illustrated.
WRITE Command Byte and 2 Data Bytes
WRITE Command Byte and no Data Bytes
2.7
READ Operation
A data request from a master to a slave is initiated by sending an address byte including a data direction
bit set to ‘1’ (READ). The slave answers by sending data from the interface output registers. The master
must generate the transmission clock for the following: SCL, acknowledges after each data byte (except
after the last one), and the stop condition at the end. A data request is handled by thedigital pressure
measuring cell’s interface module and consequently does not interrupt the current process of the internal
micro-controller.
Read 2 (+n) Data Bytes
2.8
Data bytes
The data registers of the digital pressure measuring cell consists always of 2 bytes. The device always
returns a status byte before sending the data bytes. The status byte can be for example the reading com-
mand. So the slave returns 3 bytes when reading one register.
5
4
3
2
1
0
W
A
7
6
5
0
3
2
1
0
A
15 14 13 12 11 10 9
8
A
7
6
5
4
3
2
1
0
A
S
S
6
Device Slave Address [6:0]
Command Byte [7:0]
Data Byte [15:8]
Data Byte [7:0]
5
4
3
2
1
0
W
A
7
6
5
0
3
2
1
0
A
S
6
Device Slave Address [6:0]
Command Byte [7:0]
S
S
Start/Stop condition
6
Device slave address (example: Bit 5)
W Read/Write Bit (example: Write=0)
5
Command Bit (example: Bit 5)
4
Data Bit (example: Bit 4)
A
Acknowledge (ACK)
5
4
3
2
1
0
R
A
S
6
15 14 13 12 11 10 9
8
A
7
6
5
4
3
2
1
0
A
7
6
5
4
3
2
1
0
N
S
Device Slave Address [6:0]
Data Byte [15:8]
Data Byte [7:0]
n Data Byte
th
obligatory
optional
obl.
S
Start/Stop condition
6
Device slave address (example: Bit 6)
W Read/Write Bit (example: Write=1)
5
Command/Data Bit (example: Bit 5)
A
Acknowledge (ACK)
N
No Acknowledge (NACK)
Summary of Contents for 405101
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Page 12: ...2 I C communication 12...
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