I2C Operation Modes
1775
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Inter-Integrated Circuit (I2C) Module
31.3.5 Low Power Mode
The I2C module can be placed in low-power mode by a global low-power mode initiated by the system (by
writing to the Peripheral Power-Down Set Register in the Peripheral Central Resource (PCR) module.
In effect, low-power mode shuts down all the clocks to the module. In global low-power mode, no registers
are visible to the software; nothing can be written to or read from any register.
31.3.6 Free Run Mode
The I2C module can be placed in free run mode when the FREE bit (I2CMDR.14) is set to 1. This bit is
primarily used on an emulator when encountering a breakpoint while debugging software. When the FREE
bit is set to 0, the I2C responds differently depending on whether the SCL is high or low. If the SCL is low,
the I2C stops immediately and keeps driving the SCL low whether the I2C is the master transmitter or
receiver. If the SCL is high, the I2C waits until the SCL becomes a low and then stops. If the I2C is a
slave, it stops when the transmission/reception completes.
31.3.7
Ignore NACK Mode
The I2C module can be placed in the ignore NACK mode by setting the IGNACK bit in the I2CEMDR
register. This mode allows an I2C module that is configured as a master transmitter to ignore a NACK
from a slave device that is not capable of generating a proper ACK signal.