Functional Description
1525
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Inter-Integrated Circuit (I2C) Interface
22.3.2.1 Standard and Fast Modes
Standard and Fast modes are selected using a value in the I2C Master Timer Period (I2CMTPR) register
that results in an SCL frequency of 100 kbps for Standard mode or 400 kbps for Fast mode.
The I2C clock rate is determined by the parameters CLK_PRD, TIMER_PRD, SCL_LP, and SCL_HP
where:
CLK_PRD
is the system clock period
SCL_LP
is the low phase of SCL (fixed at 6)
SCL_HP
is the high phase of SCL (fixed at 4)
TIMER_PRD
is the programmed value in the I2CMTPR register.
The I2C clock period is calculated as follows:
SCL_PERIOD = 2 × (1 + TIMER_PRD) × ( SCL_HP) × CLK_PRD
For example:
CLK_PRD
= 50 ns
TIMER_PRD
= 2
SCL_LP
=6
SCL_HP
=4
yields a SCL frequency of:
1/SCL_PERIOD
= 333 Khz
gives examples of the timer periods that should be used to generate both standard and fast
mode SCL frequencies based on various system clock frequencies.