I2Cx_SDA
I2Cx_SCL
START
condition (S)
condition (P)
STOP
Data line
stable data
Change of data
allowed
I2Cx_SDA
I2Cx_SCL
Architecture
993
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Inter-Integrated Circuit (I2C) Module
22.2.4.2 Data Validity
The data on I2Cx_SDA must be stable during the high period of the clock (see
). The high or
low state of the data line, I2Cx_SDA, can change only when the clock signal on I2Cx_SCL is low.
Figure 22-5. Bit Transfer on the I2C-Bus
22.2.5 START and STOP Conditions
The I2C peripheral can generate START and STOP conditions when the peripheral is configured to be a
master on the I2C-bus, as shown in
:
•
The START condition is defined as a high-to-low transition on the I2Cx_SDA line while I2Cx_SCL is
high. A master drives this condition to indicate the start of a data transfer.
•
The STOP condition is defined as a low-to-high transition on the I2Cx_SDA line while I2Cx_SCL is
high. A master drives this condition to indicate the end of a data transfer.
The I2C-bus is considered busy after a START condition and before a subsequent STOP condition. The
bus busy (BB) bit of ICSTR is 1. The bus is considered free between a STOP condition and the next
START condition. The BB is 0.
The master mode (MST) bit and the START condition (STT) bit in ICMDR must both be 1 for the I2C
peripheral to start a data transfer with a START condition. The STOP condition (STP) bit must be set to 1
for the I2C peripheral to end a data transfer with a STOP condition. A repeated START condition
generates when BB is set to 1 and STT is also set to 1. See
for a description of ICMDR
(including the MST, STT, and STP bits).
Figure 22-6. I2C Peripheral START and STOP Conditions