DS1621 datasheet(10/16 Pages) DALLAS

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DS1621

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102299

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 TOUT 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 TOUT 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 of the counter byte. This command is valid only if R/ W is “1”.

Read Slope [A9h]

This command reads the value of the slope counter byte from the DS1621. 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

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