Datasheet

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Single Bus Description
AM2320 device uses a simplified single-bus communication. Single bus that only one data line,
the data exchange system, the control by the data line is completed. Device (microprocessor) through
an open-drain or tree-state port is connected to the data line to allow the device when not
transmitting data to release the bus, and let other devices use the bus; single bus usually requires an
external 5.1k
Ω
of approximately pull-up resistors, so that when the bus is idle, the state is high.
Because they are master-slave structure, only when the host calls the sensor, the sensor will be
answered, so the host access to the sensor must strictly follow the sequence of a single bus, if there is
a sequence of confusion, the sensor will not respond to the host.
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Single bus transfer data definitions
SDA and AM2320 microprocessors for communication and synchronization between using single
bus data format, a 40-bit data transfer, high first-out. , The communication format specific
communication sequence shown in Figure 20 are shown in Table 9.
Figure 20: AM2320 single bus communication protocol
Table 9: AM2320 communication format
Name
Single bus format definition
Start signal
The microprocessor data bus (SDA) low period (at least 800μs)
]1[
, to prepare the data notification sensor
Response signal
Sensor data bus (SDA) low 80
μ
s, 80
μ
s followed by a high signal in response to the initial host
Data Format
Upon receipt of the host start signal from the data bus disposable sensor (SDA) string of 40-bit data, the high
first-out
Humidity
Humidity resolution is 16Bit, the previous high; strings out of the humidity sensor is 10 times the actual
humidity values.
Temperature
Temperature resolution is 16Bit, the previous high; sensor string temperature value is 10 times the actual
temperature value;
Temperature highest bit (Bit15) is equal to 1 indicates a negative temperature, the temperature highest bit
(Bit15) is equal to 0 indicates a positive temperature;
In addition to the temperature of the highest bit (Bit14 ~ Bit0) indicates the temperature value.
Parity bit
Parity bit = humidity high temperature + humidity + high + low temperature low
[1] For details, see 7.3
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Single bus data sample calculation
Example 1: 40 of the received data:
0000 0010 1001 0010 0000 0001 0000 1101 1010 001
High humidity 8 Low humidity 8 High temperature 8 Low temperature8 Parity bit
Calculated as follows:
0000 0010+1001 0010 +0000 0001+0000 1101= 1010 0010 (Parity bit)
Receive data is correct: