DS18S20 查看數據表（PDF） - Maxim Integrated
零件编号
产品描述 (功能)
生产厂家
DS18S20 Datasheet PDF : 23 Pages
| |||
Figure 2. Temperature Register Format
DS18S20
LS BYTE
MS BYTE
S = SIGN
BIT 7
26
BIT 15
S
BIT 6
25
BIT 14
S
BIT 5
24
BIT 13
S
BIT 4
23
BIT 12
S
BIT 3
22
BIT 11
S
BIT 2
21
BIT 10
S
BIT 1
20
BIT 9
S
BIT 0
2-1
BIT 8
S
Table 1. Temperature/Data Relationship
TEMPERATURE
(°C)
DIGITAL OUTPUT
(BINARY)
+85.0*
0000 0000 1010 1010
+25.0
0000 0000 0011 0010
+0.5
0000 0000 0000 0001
0
0000 0000 0000 0000
-0.5
1111 1111 1111 1111
-25.0
1111 1111 1100 1110
-55.0
1111 1111 1001 0010
*The power-on reset value of the temperature register is +85°C.
DIGITAL OUTPUT
(HEX)
00AAh
0032h
0001h
0000h
FFFFh
FFCEh
FF92h
OPERATION—ALARM SIGNALING
After the DS18S20 performs a temperature conversion, the temperature value is compared to the user-
defined two’s complement alarm trigger values stored in the 1-byte TH and TL registers (see Figure 3).
The sign bit (S) indicates if the value is positive or negative: for positive numbers S = 0 and for negative
numbers S = 1. The TH and TL registers are nonvolatile (EEPROM) so they will retain data when the
device is powered down. TH and TL can be accessed through bytes 2 and 3 of the scratchpad as explained
in the Memory section.
Figure 3. TH and TL Register Format
BIT 7
S
BIT 6
26
BIT 5
25
BIT 4
25
BIT 3
25
BIT 2
22
BIT 1
21
BIT 0
20
Only bits 8 through 1 of the temperature register are used in the TH and TL comparison since TH and TL
are 8-bit registers. If the measured temperature is lower than or equal to TL or higher than TH, an alarm
condition exists and an alarm flag is set inside the DS18S20. This flag is updated after every temperature
measurement; therefore, if the alarm condition goes away, the flag will be turned off after the next
temperature conversion.
The master device can check the alarm flag status of all DS18S20s on the bus by issuing an Alarm Search
[ECh] command. Any DS18S20s with a set alarm flag will respond to the command, so the master can
determine exactly which DS18S20s have experienced an alarm condition. If an alarm condition exists and
the TH or TL settings have changed, another temperature conversion should be done to validate the alarm
condition.
4 of 23
Share Link: 