7.5.2.1 F/S Mode Protocol
The following steps explain a complete transaction in F/S mode.
1. The controller initiates data transfer by generating a start condition.
condition is when a high-to-low transition occurs on the SDA line while SCL is high. All I
2
C-compatible
devices recognize a start condition.
2. The controller then generates the SCL pulses, and transmits the 7-bit address and the read/write direction
bit (R/W) on the SDA line. During all transmissions, the controller makes sure that data are valid.
the clock pulse. All devices recognize the address sent by the controller and compare the address to the
respective internal fixed address. Only the target device with a matching address generates an acknowledge
by pulling the SDA line low during the entire high period of the 9th SCL cycle (see also
). When
the controller detects this acknowledge, the communication link with a target has been established.
3. The controller generates further SCL cycles to transmit (R/W bit 0) or receive (R/W bit 1) data to the target.
In either case, the receiver must acknowledge the data sent by the transmitter. The acknowledge signal can
be generated by the controller or by the target, depending on which is the receiver. The 9-bit valid data
sequences consists of eight data bits and one acknowledge-bit, and can continue as long as necessary.
4.
shows that to signal the end of the data transfer, the controller generates a stop condition by
pulling the SDA line from low-to-high while the SCL line is high. This action releases the bus and stops the
communication link with the addressed target. All I
2
C-compatible devices recognize the stop condition. Upon
receipt of a stop condition, the bus is released, and all target devices then wait for a start condition followed
by a matching address.
SCL
Stop
condition
SDA
Start
condition
S
P
Figure 7-19. Start and Stop Conditions
SCL
Data line stable
Data valid
SDA
Change of data
allowed
Figure 7-20. Bit Transfer on the I
2
C Bus
DAC53001, DAC53002, DAC63001, DAC63002
SLASF48 – MAY 2022
Copyright © 2022 Texas Instruments Incorporated
49
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