ms4525do Measurement Specialties, ms4525do Datasheet - Page 14

• Manufacturer Part Number: ms4525do
• Description: Pcb Mounted Pressure Transducers
• Manufacturer: Measurement Specialties

MS4525DO
Figure 1.6 – I2C Measurement Packet Reads
1.6.1 I2C Read_DF (Data Fetch)
For Data Fetch commands, the number of data bytes returned by the sensor is determined by when the
master sends the NACK and stop condition. For the Read_DF3 data fetch command (Data Fetch 3 Bytes; see
example 3 in Figure 1.6), the sensor returns three bytes in response to the master sending the slave address
and the READ bit (1): two bytes of bridge data with the two status bits as the MSBs and then 1 byte of
temperature data (8-bit accuracy). After receiving the required number of data bytes, the master sends the
NACK and stop condition to terminate the read operation. For the Read_DF4 command, the master delays
sending the NACK and continues reading an additional final byte to acquire the full corrected 11-bit temperature
measurement. In this case, the last 5 bits of the final byte of the packet are undetermined and should be
masked off in the application. The Read_DF2 command is used if corrected temperature is not required. The
master terminates the READ operation after the two bytes of bridge data (see example 2 in Figure 1.6).
The two status bits (Bit 15 and Bit 14) give an indication of stale or valid data depending on their value. A
returned value of 00 indicate “normal operation and good data packet” and a returned value of 10 indicate “stale
data that has been already fetched”. Users that use “status bit” polling should select a frequency slower than
20% more than the response time.
MS4525DO
www.meas-spec.com
January 2011
14/17