DS1371

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Figures 6 and 7 detail how data transfer is accomplished on the 2-wire bus. Depending upon the state of

the R/W bit, two types of data transfer are possible:

Data transfer from a master transmitter to a slave receiver. The first byte transmitted by the master is

the slave address. Next follows a number of data bytes. The slave returns an acknowledge bit after each

received byte.

Data transfer from a slave transmitter to a master receiver. The first byte (the slave address) is

transmitted by the master. The slave then returns an acknowledge bit. Next follows a number of data

bytes transmitted by the slave to the master. The master returns an acknowledge bit after all received

bytes other than the last byte. At the end of the last received byte, a “not acknowledge” is returned.

The master device generates all of the serial clock pulses and the START and STOP conditions. A

transfer is ended with a STOP condition or with a repeated START condition. Since a repeated START

condition is also the beginning of the next serial transfer, the bus is not released.

The DS1371 can operate in the following two modes:

Slave receiver mode (DS1371 write mode). Serial data and clock are received through SDA and SCL.

After each byte is received, an acknowledge bit is transmitted. START and STOP conditions are

recognized as the beginning and end of a serial transfer. Address recognition is performed by hardware

after reception of the slave address and direction bit. The slave address byte is the first byte received after

the START condition is generated by the master. The slave address byte contains the 7-bit DS1371

address, which is 1101000, followed by the direction bit (R/W), which for a write is a 0. After receiving

and decoding the slave address byte the DS1371 outputs an acknowledge on SDA. After the DS1371

acknowledges the slave address + write bit, the master transmits a word address to the DS1371. This sets

the register pointer on the DS1371, with the DS1371 acknowledging the transfer. The master may then

transmit zero or more bytes of data, with the DS1371 acknowledging each byte received. The register

pointer increments after each byte is transferred. The master generates a STOP condition to terminate the

data write.

Slave transmitter mode (DS1371 read mode). The first byte is received and handled as in the slave

receiver mode. However, in this mode, the direction bit indicates that the transfer direction is reversed.

Serial data is transmitted on SDA by the DS1371 while the serial clock is input on SCL. START and

STOP conditions are recognized as the beginning and end of a serial transfer. Address recognition is

performed by hardware after reception of the slave address and direction bit. The slave address byte is the

first byte received after the START condition is generated by the master. The slave address byte contains

the 7-bit DS1371 address, which is 1101000, followed by the direction bit (R/W), which for a read is a 1.

After receiving and decoding the slave address byte, the DS1371 outputs an acknowledge on SDA. The

DS1371 then begins to transmit data starting with the register address pointed to by the register pointer. If

the register pointer is not written to before the initiation of a read mode the first address that is read is the

last one stored in the register pointer. The DS1371 must receive a “not acknowledge” to end a read.