DS1621 Datasheet, PDF (10/16 Pages) Dallas Semiconductor – Digital Thermometer and Thermostat

DS1621
COMMAND SET
Data and control information is read from and written to the DS1621 in the format shown in Figure 5. To
write to the DS1621, the master will issue the slave address of the DS1621 and the R/ W bit will be set to
“0”. After receiving an acknowledge, the bus master provides a command protocol. After receiving this
protocol, the DS1621 will issue an acknowledge and then the master may send data to the DS1621. If the
DS1621 is to be read, the master must send the command protocol as before and then issue a repeated
START condition and the control byte again, this time with the R/ W bit set to “1” to allow reading of the
data from the DS1621. The command set for the DS1621 as shown in Table 3 is as follows:
Read Temperature [AAh]
This command reads the last temperature conversion result. The DS1621 will send 2 bytes, in the format
described earlier, which are the contents of this register.
Access TH [A1h]
If R/ W is “0” this command writes to the TH (HIGH TEMPERATURE) register. After issuing this
command, the next 2 bytes written to the DS1621, in the same format as described for reading
temperature, will set the high temperature threshold for operation of the T_OUT output. If R/ W is “1” the
value stored in this register is read back.
Access TL [A2h]
If R/ W is “0” this command writes to the TL (LOW TEMPERATURE) register. After issuing this
command, the next 2 bytes written to the DS1621, in the same format as described for reading
temperature, will set the high temperature threshold for operation of the T_OUT output. If R/ W is “1” the
value stored in this register is read back.
Access Config [ACh]
If R/ W is “0” this command writes to the configuration register. After issuing this command, the next
data byte is the value to be written into the configuration register. If R/ W is “1” the next data byte read is
the value stored in the configuration register.
Read Counter [A8h]
This command reads the value Count_Remain. This command is valid only if R/ W is “1”.
Read Slope [A9h]
This command reads the value Count_Per_C. This command is valid only if R/ W is “1”.
Start Convert T [EEh]
This command begins a temperature conversion. No further data is required. In one-shot mode the
temperature conversion will be performed and then the DS1621 will remain idle. In continuous mode this
command will initiate continuous conversions.
Stop Convert T [22h]
This command stops temperature conversion. No further data is required. This command may be used to
halt a DS1621 in continuous conversion mode. After issuing this command, the current temperature
measurement will be completed and the DS1621 will remain idle until a Start Convert T is issued to
resume continuous operation.
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