Philips Semiconductors
Product specification
Low power clock/calendar
PCF8593
8.3
System configuration (see Fig.15)
A device generating a message is a ‘transmitter’, a device receiving a message is the ‘receiver’. The device that controls
the message is the ‘master’ and the devices which are controlled by the master are the ‘slaves’.
SDA
SCL
MASTER
TRANSMITTER /
RECEIVER
SLAVE
TRANSMITTER /
RECEIVER
MASTER
TRANSMITTER /
RECEIVER
SLAVE
RECEIVER
MASTER
TRANSMITTER
MBA605
Fig.15 System configuration.
The device that acknowledges must pull down the SDA
line during the acknowledge clock pulse, so that the SDA
line is stable LOW during the HIGH period of the
acknowledge related clock pulse (set-up and hold times
must be taken into consideration). A master receiver must
signal an end of data to the transmitter by not generating
an acknowledge on the last byte that has been clocked out
of the slave. In this event the transmitter must leave the
data line HIGH to enable the master to generate a stop
condition.
8.4
Acknowledge (see Fig.16)
The number of data bytes transferred between the start
and stop conditions from transmitter to receiver is
unlimited. Each byte of eight bits is followed by an
acknowledge bit. The acknowledge bit is a HIGH level
signal put on the bus by the transmitter during which time
the master generates an extra acknowledge related clock
pulse. A slave receiver which is addressed must generate
an acknowledge after the reception of each byte. Also a
master receiver must generate an acknowledge after the
reception of each byte that has been clocked out of the
slave transmitter.
DATA OUTPUT
BY TRANSMITTER
not acknowledge
acknowledge
DATA OUTPUT
BY RECEIVER
SCL FROM
1
2
8
9
MASTER
S
clock pulse for
acknowledgement
START
CONDITION
MBC602
Fig.16 Acknowledgment on the I2C-bus.
1997 Mar 25
16
NXP [ NXP ]
