HS300x-MC1 Datasheet

R36DS0018EU0101 Rev.1.01

Jul 12, 2022

Page 13

5.6

Data Fetch (DF)

At the end of a measurement cycle, valid data can be fetched. The status bits of the DF results can be used to

detect if the data is valid or stale (see “Status Bits”); otherwise, wait for the measurements to complete before

performing the DF.

The DF command starts with the 7-bit slave address followed by an eighth bit = 1 (READ). The HS300x-MC1 as

a slave sends an acknowledge (ACK) indicating success.

The number of data bytes returned by the HS300x-MC1 is determined by when the master sends the NACK and

STOP condition. The full 14 bits of the humidity data are fetched in the first two bytes. The two MSBs of the first

byte are the status bits.

The 14 bits of temperature data follow the humidity data. The last two bits (LSBs) of the fourth data byte are

undetermined and should be masked off. In the event that the temperature data is not needed, the read can be

terminated by sending a NACK after the second byte.

Alternatively, if only 8-bit resolution is desired for the temperature output, the read can be terminated after the 3rd

byte by issuing a NACK followed by a stop bit. The measurement time depends on the configured sensor

resolution. The following table lists examples when the resolutions for the relative humidity and temperature

measurements are the same. For different relative humidity and temperature resolution settings, the

measurement times in 3 should be used, along with the 0.1ms wake-up time.

For example, an 8-bit relative humidity measurement and a 12-bit temperature measurement results in a total

measurement time of:

0.1 ms + 0.55 ms + 4.5 ms = 5.15 ms.

RH+T measurement times (including wake-up time) at different resolution settings.

Resolution[1] (Bits)

Measurement Time (ms)

8

1.20

10

2.72

12

9.10

14

33.90

1.

Same resolutions are assumed for both relative humidity and temperature.

Figure 16. Data Fetch

Device Slave Address [6:0]

Humidity Data [13:8]

Humidity Data [7:0]

Humidity Data [13:8]

Humidity Data [7:0]

Temp. Data [15:8]

Slave Address Bit (MSB first)

Commandor Data Bit (Example: Bit 2)

Status Bit

Start Condition

Stop Condition

Acknowledge (ACK)

Not Acknowledge

Read/Write

(NACK)

(Read = 1)

S

S

R

N

Wait for

Slave ACK

Master ACK

Master ACK

Master NACK

14 13

11

12

10

8

9

A

6 5

7

3

4

2

N

1 0

S

1

S

0 0

1

0

0

R

(1)

0

A 15

1

S

0

1 0

R

(1)

0

A

14 13

15

11

12

10

8

9

A

6 5

7

3

4

2

A

1 0

14 13

15

11

12

10

A

9 8

0

0

Device Slave Address [6:0]

A

2

Temp. Data [7:2]

6 5

7

3

4

2

S

N

1 0

Mask [1:0]