DS1631S+T&R【PDF 12/16 页】IC THERMOMETER DIG HI-PREC 8SOIC

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DS1631/DS1631A/DS1731

12 of 15

Figure 8. START, STOP, AND ACK SIGNALS

GENERAL 2-WIRE INFORMATION

All data is transmitted MSb first over the 2-wire bus.

One bit of data is transmitted on the 2-wire bus each SCL period.

A pullup resistor is required on the SDA line and, when the bus is idle, both SDA and SCL must remain

in a logic-high state.

All bus communication must be initiated with a START condition and terminated with a STOP

condition. During a START or STOP is the only time SDA is allowed to change states while SCL is

high. At all other times, changes on the SDA line can only occur when SCL is low: SDA must remain

stable when SCL is high.

After every 8-bit (1-byte) transfer, the receiving device must answer with an ACK (or NACK), which

takes one SCL period. Therefore, nine clocks are required for every one-byte data transfer.

INITIATING 2-WIRE COMMUNICATION

To initiate 2-wire communication, the master generates a START followed by a control byte containing

the DS1631, DS1631A, or DS1731 slave address. The R/W?/SPAN>?/SPAN> bit of the control byte must be a 0 (write)

since the master next writes a command byte. The DS1631/DS1631A/DS1731 responds with an ACK

after receiving the control byte. This must be followed by a command byte from the master, which

indicates what type of operation is to be performed. The DS1631/DS1631A/DS1731 again respond with

an ACK after receiving the command byte.

If the command byte is a Start Convert T or Stop Convert T command (see Figure 9a), the transaction is

finished, and the master must issue a STOP to signal the end of the communication sequence. If the

command byte indicates a write or read operation, additional actions must occur as explained in the

following sections.

2-WIRE WRITES

The master can write data to the DS1631/DS1631A/DS1731 by issuing an Access Config, Access TH, or

Access TL command following the control byte (see Figures 9b and 9d). Since the R/W?/SPAN>?/SPAN> bit in the control

byte was a 0 (write), the DS1631/DS1631A/DS1731 are already prepared to receive data. Therefore,

after receiving an ACK in response to the command byte, the master device can immediately begin

transmitting data. When writing to the configuration register, the master must send one byte of data, and

when writing to the T

or T

registers the master must send two bytes of data. After receiving each data

byte, the DS1631/DS1631A/DS1731 respond with an ACK, and the transaction is finished with a STOP

from the master.

SCL

SDA

START

Condition

STOP

Condition

ACK (or NACK)

From Receiver

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