Datasheet

DS1626/DS1726
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CPU BIT AND STAND-ALONE THERMOSTAT OPERATION
In stand-alone thermostat mode, DS1626/DS1726 thermostat functionality can be used without requiring
a microcontroller to start/stop temperature conversions. The CPU bit in the configuration register
determines if stand-alone mode is enabled.
When CPU = 1 stand-alone mode is disabled, and the only way to start/stop temperature conversions is
by using a microcontroller to transmit Start Convert T and Stop Convert T commands, respectively.
Stand-alone mode is enabled when CPU = 0. In this mode, when RST = 0 the CLK/CNV pin operates as
a control signal to start and stop temperature measurements. Driving CLK/CNV low initiates continuous
temperature conversions that will continue until CLK/CNV is brought high again. If the CLK/CNV pin is
driven low and then returned to a high state in less than 10ms, only one temperature conversion will be
performed after which the DS1626/DS1726 will return to a low-power idle state (i.e., one-shot operation).
Note that when stand-alone mode is enabled, the 1SHOT bit in the configuration register is ignored, and
only the CLK/CNV signal determines whether continuous or one-shot conversions take place.
Since T
H
, T
L
, and the CPU bit are stored in EEPROM, the DS1626/DS1726 can be preprogrammed for
stand-alone operation. If desired, the CLK/CNV and RST pin can be connected to GND so the
DS1626/DS1726 will automatically begin taking temperature measurements at power-up
Normal bus communication with the DS1626/DS1726 can still take place in stand-alone mode when
RST = 1. When communication is initiated, stand-alone conversions are automatically halted. If during
the bus communication continuous temperature conversions are started using the Start Convert T
command, they can only be stopped by issuing a Stop Convert T command.
Figure 5. THERMOSTAT OUTPUT OPERATION
T
L
T
H
TEMP
LOGIC 0
LOGIC 1
T
COM
TEMP
LOGIC 0
LOGIC 1
T
HIGH
TEMP
LOGIC 0
LOGIC 1
T
LOW