User manual

AHHYTM_E2.2.1
12/23
Application Note
Humidity Module
HYT
Parameter Symbol Min Max Unit
SCL clock frequency fSCL 100 400 kHz
Start condition hold time relative to SCL edge tHDSTA 0.1 µs
Minimum SCL clock low width 1 tLOW 0.6 µs
Minimum SCL clock high width 1 tHIGH 0.6 µs
Start condition setup time relative to SCL edge tSUSTA 0.1 µs
Data hold time on SDA relative to SCL edge tHDDAT 0 µs
Data setup time on SDA relative to SCL edge tSUDAT 0.1 µs
Stop condition setup time on SCL tSUSTO 0.1 µs
Bus free time between stop condition and start condition tBUS 1 µs
There are two I
2
C commands for the user to access the humidity module:
Command Description
‚Data Fetch‘ (DF) Fetch the last measured value of Humidity / Temperature
‚Measuring Request‘ (MR) Start a measuring cycle
In the initial condition, the humidity module is in sleep mode to minimize the current consumption. A new
measurement is carried out only after the command measuring request (MR) is received. Access to the status
bits and measured values is made by the data fetch command. After the measuring cycle has been completely
processed, the ready status bit is set and the current measured values are available. To determine if the measuring
cycle has been already nished, the output registers may be cyclically polled. If the access to the measured values
takes place too early, the measured values of the previous measuring cycle are transferred and the stale status bit is
set.
4.2 MR (Measurement Requests)
By a measurement request command, the sleep mode is terminated and the humidity module executes a
measurement cycle. The measuring cycle begins with the temperature measurement, followed by humidity
measurement, digital signal processing (linearizing, temperature compensation) and nally writes the processed
measured values into the output register.