Datasheet

DS1775
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Figure 2. O.S. Output Transfer Function
Regardless of the mode chosen, the O.S. output is open-drain and the active state is set in the
configuration register. The power-up default is active low. See the Programming section for instructions
in adjusting the thermostat setpoints, thermostat mode, and O.S. active state.
Programming
There are three areas of interest in programming the DS1775: the configuration register, the T
OS
register,
and the T
HYST
register. All programming is done via the 2-wire interface by setting the pointer to the
appropriate location. Table 3 illustrates the pointer settings for the four registers of the DS1775.
Table 3. Pointer Register Structure
POINTER
ACTIVE REGISTER
00h
Temperature (default)
01h
Configuration
02h
T
HYST
03h
T
OS
The DS1775 powers up with the temperature register selected. If the host wishes to change the data
pointer, it simply addresses the DS1775 in the write mode (R/
W
= 0), receives an acknowledge, and
writes the 8 bits that correspond to the new desired location. The last pointer location is always
maintained so that consecutive reads from the same register do not require the host to always provide a
pointer address. The only exception is at power-up, in which case the pointer is always set to 00h, the