SAA7740 Philips Semiconductors, SAA7740 Datasheet - Page 21

• Manufacturer Part Number: SAA7740
• Description: Digital Audio Processing IC DAPIC
• Manufacturer: Philips Semiconductors

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Philips Semiconductors
I
The I
between different ICs or modules. The two lines are the
serial data line (SDA) and the serial clock line (SCL). Both
lines must be connected to the supply rail via a pull-up
resistor when connected to the output stages of a
microcontroller. Data transfer can only be initiated when
the bus is not busy. Full details of the I
the document “The I
document may be ordered using the code
9398 393 40011.
Bit transfer
One data bit is transferred during each clock pulse.
The data on the SDA line must remain stable during the
HIGH period of the clock pulses as changes in the data line
at this time will be interpreted as control signals.
The maximum clock frequency is 100 kHz (see Fig.12).
START and STOP condition
In the START and STOP condition the data and clock lines
remain HIGH when the bus is not busy. A HIGH-to-LOW
transition on the data line, while the clock is HIGH, is
defined as the START condition (S). A LOW-to-HIGH
transition on the data line, while the clock is HIGH, is
defined as the STOP condition (P); (see Fig.13).
1997 May 30
2
C-BUS PROTOCOL
Digital Audio Processing IC (DAPIC)
2
C-bus is intended for 2-way, 2-line communication
2
C-bus and how to use it” . This
SDA
SCL
2
C-bus are given in
Fig.12 Bit transfer on the I
data valid
data line
stable
allowed
change
of data
21
Data transfer
A device generating a message is a ‘transmitter’, a device
receiving a message is a ‘receiver’. The device that
controls the message is the ‘master’ and the devices which
are controlled by the device are the ‘slaves’ (see Fig.14).
Acknowledge
The number of data bytes that are transferred between the
START and STOP conditions, from transmitter to receiver,
is unlimited. Each byte is followed by an acknowledge bit.
The acknowledge bit is a HIGH level bit placed on the bus
by the transmitter, whereas the master generates an extra
acknowledge bit which is related to the clock pulse. A slave
receiver which is addressed must generate an
acknowledge bit after the reception of each byte.
The master must also generate an acknowledge bit after
the reception of each byte that has been clocked out of the
slave transmitter.
The device that acknowledges has to 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 also be taken into account. A master receiver must
signal an end-of-data to the transmitter. This is achieved
by not generating an acknowledge on the last byte that has
been clocked out of the slave. In this condition the
transmitter must leave the data line HIGH to enable the
master to generate a STOP condition (see Fig.15).
2
C bus.
MLC160
Product specification
SAA7740H