I2Cx_S2 field descriptions (continued)
Field
Description
0
EMPTY
Empty flag
Indicates if the Tx or Rx buffer is empty.
0
Tx or Rx buffer is not empty and cannot be written to, that is new data cannot be loaded into the
buffer.
1
Tx or Rx buffer is empty and can be written to, that is new data can be loaded into the buffer.
36.5 Functional description
This section provides a comprehensive functional description of the I2C module.
36.5.1 I2C protocol
The I2C bus system uses a serial data line (SDA) and a serial clock line (SCL) for data
transfers.
All devices connected to it must have open drain or open collector outputs. A logic AND
function is exercised on both lines with external pull-up resistors. The value of these
resistors depends on the system.
Normally, a standard instance of communication is composed of four parts:
1. START signal
2. Slave address transmission
3. Data transfer
4. STOP signal
The STOP signal should not be confused with the CPU STOP instruction. The following
figure illustrates I2C bus system communication.
Chapter 36 Inter-Integrated Circuit (I2C)
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
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