DS1631 Datasheet, PDF (13/15 Pages) National Semiconductor (TI) – CMOS Dual Peripheral Drivers

DS1631/DS1631A/DS1731
2-WIRE READS
The master can read data from the DS1631/DS1631A/DS1731 by issuing an Access Config, Access TH,
Access TL, or Read Temperature command following the control byte (see Figures 9c and 9e). After
receiving an ACK in response to the command, the master must generate a repeated START followed by
a control byte with the same slave address as the first control byte. However, this time the R/¯W¯ bit must
be a 1, which tells the DS1631/DS1631A/DS1731 that a “read” is being performed. After the
DS1631/DS1631A/DS1731 send an ACK in response to this control byte, it begins transmitting the
requested data on the next clock cycle. One byte of data will be transmitted when reading from the
configuration register after which the master must respond with a NACK followed by a STOP. For two-
byte reads (i.e., from the Temperature, T_H, or T_L register), the master must respond to the first data byte
with an ACK and to the second byte with a NACK followed by a STOP. If only the most significant byte
of data is needed, the master can issue a NACK followed by a STOP after reading the first data byte.
COMMAND SET
The DS1631/DS1631A/DS1731 command set is detailed below:
Start Convert T [ 51h ]
Initiates temperature conversions. If the part is in one-shot mode (1SHOT = 1), only one conversion is
performed. In continuous mode (1SHOT = 0), continuous temperature conversions are performed until a
Stop Convert T command is issued.
Stop Convert T [ 22h ]
Stops temperature conversions when the device is in continuous conversion mode (1SHOT = 0).
Read Temperature [ AAh ]
Reads last converted temperature value from the 2-byte temperature register.
Access TH [ A1h ]
Reads or writes the 2-byte T_H register.
Access TL [ A2h ]
Reads or writes the 2-byte T_L register.
Access Config [ ACh ]
Reads or writes the 1-byte configuration register.
Software POR [ 54h ]
Initiates a software power-on-reset (POR), which stops temperature conversions and resets all registers
and logic to their power-up states. The software POR allows the user to simulate cycling the power
without actually powering down the device.
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