Rainbow Electronics DS1339 - Manual (Page 12)

DS1339
12 of 18
Figure 7. DATA TRANSFER ON 2-WIRE SERIAL BUS
Depending upon the state of the R/ W bit, two types of data transfer are possible:
1) 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 is transferred with the most significant bit (MSB) first.
2) 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. This is followed by the slave
transmitting a number of data bytes. 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. Data is transferred
with the MSB first.