DS1920 4EH <write data into 2 at addresses 2 and 3 (TH and bytes at addr...

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Smutek to uczucie, jak gdyby się tonęło, jak gdyby grzebano cię w ziemi.

2 and
TL temperature triggers).
addr. 3>
Copy Scratchpad
Copies Scratchpad into
48H
strong pullup
2
nonvolatile memory
(addresses 2 and 3 only).
Recall
Recalls values stored in
B8H
idle
nonvolatile memory into
scratchpad (temperature
triggers).
NOTES:
1. Temperature conversion takes up to 0.5 seconds. After receiving the Convert Temperature command, the data line for the DS1920 must be held high for at least 0.5 seconds to provide power during the conversion process. As such, no other activity may take place on the 1-Wire bus for at least this period after a Convert Temperature command has been issued.
2. After receiving the Copy Scratchpad command, the data line for the DS1920 must be held high for at least 10 ms to provide power during the copy process. As such, no other activity may take place on the 1-Wire bus for at least this period after a Copy Scratchpad command has been issued.
READ/WRITE TIMING DIAGRAM Figure 11
Write-1 Time Slot
60 µs ≤ tSLOT < 120 µs
RESISTOR
1 µs ≤ tLOW1 < 15 µs
MASTER
1 µs ≤ tREC < ∞
17 of 22
DS1920
READ/WRITE TIMING DIAGRAM (cont’d) Figure 11
Write-0 Time Slot
60 µs ≤ tLOW0 < tSLOT < 120 µs
1 µs ≤ tREC < ∞
Read-Data Time Slot
60 µs ≤ tSLOT < 120 µs
RESISTOR
1 µs ≤ tLOWR < 15 µs
0
MASTER
≤ tRELEASE < 45 µs
1 µs ≤ tREC < ∞
DS1920
tRDV = 15 µs
tSU < 1 µs
18 of 22
DS1920
MEMORY FUNCTION EXAMPLE Table 3
Example: Bus Master initiates temperature conversion, then reads temperature.
MASTER MODE
DATA (LSB FIRST)
COMMENTS
TX
Reset
Reset pulse( 480-960 µs)
RX
Presence
Presence pulse
TX
55H
Issue "Match ROM" command
TX
<64-bit ROM code>
Issue address for DS1920
TX
44H
Issue "Convert Temperature" command TX
<DATA LINE HIGH>
Data line is held high for at least 0.5 seconds by bus master to allow conversion to complete.
TX
Reset
Reset pulse
RX
Presence
Presence pulse
TX
55H
Issue "Match ROM" command
TX
<64-bit ROM code>
Issue address for DS1920
TX
BEH
Issue "Read Scratchpad" command.
RX
<9 data bytes>
Read entire scratchpad plus CRC; the master now recalculates the CRC of the eight data bytes received from the scratchpad, compares the CRC calculated and the CRC read. If they match, the master continues; if not, this read operation is repeated.
TX
Reset
Reset pulse
RX
Presence
Presence pulse, done.
19 of 22
DS1920
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
-0.5V to +7.0V
Operating Temperature
-55°C to +100°C
Storage Temperature
-55°C to +100°C
∗ This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
DC ELECTRICAL CONDITIONS
(-55°C to +100°C)
PARAMETER
SYMBOL
CONDITION
MIN
TYP
MAX
UNITS
NOTES
Pull up Voltage
VPUP
I/O Functions
2.8
5.0
6.0
V
1,2
+½°C Accurate
4.3
6.0
V
Temperature
Conversions
Logic 1
VIH
2.2
V
2
Logic 0
VIL
-0.3
+0.8
V
2, 10
DC ELECTRICAL CHARACTERISTICS (-55°C to +100°C; VPUP=4.3V to 6.0V) PARAMETER
SYMBOL
CONDITION
MIN
TYP
MAX
UNITS
NOTES
Thermometer
tERR
0°C to + 70 °C
+½
°C
11
Error
-55°C to +0°C
and + 70 °C to
SEE TYPICAL CURVE
11
+100 °C
Active Current
IDD
1000
1500
µA
3,4
Input Load
IL
5
µA
Current
Output Logic
VOL
0.4
V
2
Low @ 4 mA
CAPACITANCE
(TA =25°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
I/O (1- Wire)
CIN/OUT
800
pF
9
AC ELECTRICAL CHARACTERISTICS; TEMPERATURE CONVERSION AND
COPY SCRATCHPAD
(-55°C to +100°C; VPUP =4.3V to 6.0V) PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Temperature Conversion
tCONV
0.2
0.5
seconds
Copy Scratchpad
tCOPY
10
ms
5
20 of 22
DS1920
AC ELECTRICAL CHARACTERISTICS:
1-WIRE INTERFACE
(-55°C to +100°C; VPUP=2.8V to 6.0V) PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Time Slot
tSLOT
60
120
µs
Write 1 Low Time
tLOW1
1
15
µs
Write 0 Low Time
tLOW0
60
120
µs
Read Data Valid
tRDV
exactly 15
µs
Release Time
tRELEASE
0
15
45
µs
Read Data Setup
tSU
1
µs
8
Recovery Time
tREC
1
µs
Reset Time High
tRSTH
480
µs
Reset Time Low
tRSTL
480
4800
µs
6,7
Presence Detect High
tPDHIGH
15
60
µs
Presence Detect Low
tPDLOW
60
240
µs
NOTES:
1. Temperature conversion will work with ±2°C accuracy down to VPUP = 3.4V.
2. All voltages are referenced to ground.
3. IDD specified with low impedance pull up to 5.0V.
4. Active current refers to temperature conversion.
5. Writing to EEPROM consumes approximately 200 µA.
6. tRSTL may be up to 4800 µs. With longer times, the result of temperature conversion may get lost.
7. The reset low time should be restricted to a maximum of 960 ms, to allow interrupt signaling, otherwise it could mask or conceal interrupt pulses.
8. Read data setup time refers to the time the host must pull the 1-Wire bus low to read a bit. Data is guaranteed to be valid within 1 µs of this falling edge and will remain valid for 14 µs minimum. (15
µs total from falling edge on 1-Wire bus.)
9. Capacitance on the data contact could be 800 pF when power is first applied. If a 5kΩ resistor is used to pull up the data line to VCC , 5 µs after power has been applied, the parasite capacitance will not affect normal communications.
10. Under certain low voltage conditions VILMAX may have to be reduced to as much as 0.5V to always guarantee a presence pulse.
11. See Typical Curve for specification limits outside the 0°C to 70°C range. Thermometer error reflects sensor accuracy as tested during calibration.
21 of 22
DS1920
TYPICAL PERFORMANCE CURVE
DS1920 TEMPERATURE iButton
TRUE TEMPERATURE (°C)
Error = Reading - True Temperature
When cold, the true temperature is typically colder than the temperature reading 22 of 22

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