DS1682 Total-Elapsed-Time Recorder with Alarm

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The DS1682 can operate in the following two modes:

Slave Receiver Mode (Write Mode): Serial data and clock are received through SDA and SCL. After

each byte is received, the receiver transmits an acknowledge bit. START and STOP conditions are

recognized as the beginning and end of a serial transfer. The slave address byte is the first byte received

after the master generates a START condition. The address byte contains the 7-bit DS1682 address,

which is 1101011, followed by the direction bit (R/

W). The second byte from the master is the register

address. This sets the register pointer. The master then transmits each byte of data, with the DS1682

acknowledging each byte received. The register pointer increments after each byte is written. The master

generates a STOP condition to terminate the data write (Figure 7).

Slave Transmitter Mode (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 DS1682 while the serial clock is input on SCL. The slave address byte is the

first byte received after the master generates a START condition. The address byte contains the 7-bit

DS1682 address, followed by the direction bit (R/

W). After receiving a valid slave address byte and

direction bit, the DS1682 generates an acknowledge on the SDA line. The DS1682 begins to transmit

data on each SCL pulse starting with the register address pointed to by the register pointer. As the master

reads each byte, it must generate an acknowledge. The register pointer increments after each byte is read.

The DS1682 must receive a “not acknowledge” on the last byte to end a read (Figure 8).

Figure 7. Data Write—Slave Receiver Mode

Figure 8. Data Read—Slave Transmitter Mode

R/

W

R/

W –READ/WRITE OR DIRECTION BIT

DATA TRANSFERRED

(X + 1 BYTES + ACKNOWLEDGE)

SLAVE

ADDRESS

REGISTER

ADDRESS

S–START

A –ACKNOWLEDGE

P– STOP

DATA (n)

DATA (n + 1)

DATA (n + x)

DATA TRANSFERRED

(X + 1 BYTES + ACKNOWLEDGE)

SLAVE

ADDRESS

S—START

A—- ACKNOWLEDGE

P—- STOP

/A — NOT ACKNOWLEDGE

R/

W — READ/WRITE OR DIRECTION BIT

DATA (n)

DATA (n + 1)

DATA (n + x)

DATA (n + 2)

R/

W