DS1631 Datasheet, PDF (9/15 Pages) National Semiconductor (TI) – CMOS Dual Peripheral Drivers

DS1631/DS1631A/DS1731
and Access TL commands. When making changes to the T_H and T_L registers, conversions should first be
stopped using the Stop Convert T command if the device is in continuous conversion mode. Note that if
the thermostat function is not used, the T_H and T_L registers can be used as general-purpose NV memory.
Another thermostat feature is the temperature high and low flags (THF and TLF) in the configuration
register. These bits provide a record of whether the temperature has been greater than T_H or less than T_L
at anytime since the device was powered up. These bits power up as 0s, and if the temperature ever
exceeds the T_H register value, the THF bit is set to 1, or if the temperature ever falls below the T_L value,
the TLF bit is set to 1. Once THF and/or TLF has been set, it remains set until overwritten with a 0 by the
user or until the power is cycled.
DS1631A STAND-ALONE THERMOSTAT OPERATION
Since the DS1631A automatically begins taking temperature measurements at power-up, it can function
as a standalone thermostat (i.e., it can provide thermostatic operation without microcontroller
communication). For standalone operation, the NV T_H and T_L registers and the POL and 1SHOT bits in
the configuration register should be programmed to the desired values prior to installation. Since the
default conversion resolution at power-up is 12 bits (R1 = 1 and R0 = 1 in the configuration register), the
conversion resolution is always 12 bits during standalone thermostat operation.
Figure 5. THERMOSTAT OUTPUT OPERATION
LOGIC 1
POL = 1 (T_OUT IS ACTIVE HIGH)
T_OUT
LOGIC 0
T_L
T_H
TEMP
CONFIGURATION REGISTER
The configuration register allows the user to program various DS1631 options such as conversion
resolution, T_OUT polarity, and operating mode. It also provides information to the user about conversion
status, EEPROM activity, and thermostat activity. The configuration register is arranged as shown in
Figure 6 and detailed descriptions of each bit are provided in Table 5. This register can be read from and
written to using the Access Config command. When writing to the configuration register, conversions
should first be stopped using the Stop Convert T command if the device is in continuous conversion
mode. Note that the POL and 1SHOT bits are stored in EEPROM so they can be programmed prior to
installation is desired. All other configuration register bits are SRAM and power up in the state shown in
Table 5.
Figure 6. CONFIGURATION REGISTER
MSb
bit 6
bit 5
bit 4
bit 3
DONE THF TLF NVB R1
*NV (EEPROM)
bit 2
bit 1
LSb
R0 POL* 1SHOT*
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