DS1631S Datasheet DS1731U+, DS1631Z, DS1631 | P13-P15

DS1631/DS1631A/DS1731

13 of 15

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

, or T

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

Access TL [ A2h ]

Reads or writes the 2-byte T

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.

DS1631/DS1631A/DS1731

14 of 15

Figure 9 (a, b, c, d, e). 2-WIRE INTERFACE TIMING

THERM = DS1631, DS1631A, or DS1731

a) Issue a "Start Convert T” or “Stop Convert T” Command

A2 A1 A0

AC7C6C5C4 A

C1 C0

Control Byte

Command Byte

START

STOP

ACK

(THERM)

SCL

SDA

ACK

(THERM)

d) Write to the T

or T

A2 A1 A0 C2

SCL

SDA

S 1

Control Byte

START

ACK

(THERM)

C7 C6 C5 C4

C1 C0

Command Byte ACK

(THERM)

D6 D5

D2 D0D7D6 D5 D4

D2 D1 D0

LS Data Byte

(from Master)

MS Data Byte

(from Master)

STOP

ACK

(THERM)

ACK

(THERM)

e) Read From the Temperature, T

, or T

AD2D1D0D6 D5 D4

A2 A1 A0

AC4

C2 C1C7 C6 C5A2 A1 A0

ACK

(THERM)

Repeat

START

SCL

SDA

S 11

Control Byte

START

Command Byte

S 11

Control Byte MS Data Byte

(from THERM)

…

ACK

(THERM)

ACK

(THERM)

ACK

(Master)

D6 D4

D2 D1 D0 P

LS Data Byte

(from THERM)

STOP

…

NACK

(Master)

(THERM)

AD2D6 D5 D4

D1 D0A0

AA1 1 0 1 0

100AD7A2

b) Write to the Configuration Register

S1 100

Control ByteSTART

SCL

SDA

ACK

Command Byte

Data Byte

(from Master)

STOP

ACK

(THERM)

NA1S1 1

A2 A1 A0

010 A

100

D6 D5

D2 D1 D0

A2 A1 A0

c) Read From the Configuration Register

ACK

(THERM)

Repeat

START

SCL

SDA

Control Byte

START

Command Byte

Data Byte

(from THERM)

STOP

NACK

(Master)

Control Byte

ACK

(THERM)

ACK

(THERM)

DS1631/DS1631A/DS1731

15 of 15

OPERATION EXAMPLE

In this example, the master configures the DS1631/DS1631A/DS1731 (A

= 000) for continuous

conversions and thermostatic function.

MASTER

MODE

THERMETER*

MODE

DATA

(MSb first)

COMMENTS

TX RX START START condition from MASTER.

TX RX 90h

MASTER sends control byte with R/W¯¯ = 0.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX ACh MASTER sends Access Config command.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX 02h

MASTER writes a data byte to the configuration register to

put the THERMOMETER in continuous conversion mode

and set the T

OUT

polarity to active high.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX STOP STOP condition from MASTER.

TX RX START START condition from MASTER.

TX RX 90h

MASTER sends control byte with R/W¯¯ = 0.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX A1h MASTER sends Access TH command.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX 28h MASTER sends most significant data byte for T

= +40°C.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX 00h MASTER sends least significant data byte for T

= +40°C.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX STOP STOP condition from MASTER.

TX RX START START condition from MASTER.

TX RX 90h

MASTER sends control byte with R/W¯¯ = 0.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX A2h MASTER sends Access TL command.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX 0Ah MASTER sends most significant data byte for T

= +10°C.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX 00h MASTER sends least significant data byte for T

= +10°C.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX STOP STOP condition from MASTER.

TX RX START START condition from MASTER.

TX RX 90h

MASTER sends control byte with R/

W¯¯ = 0.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX 51h MASTER sends Start Convert T command.

RX TX ACK Acknowledge bit from THERMOMETER.

TX RX STOP STOP condition from MASTER.

*THERMOMETER = DS1631, DS1631A, or DS1731

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P16

DS1631S

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