SWRU543B January 2019 – June 2025 CC3230S , CC3230SF , CC3235MODS , CC3235MODSF , CC3235S , CC3235SF
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 and 400 kbps for fast mode.
The I2C clock rate is determined by the parameters CLK_PRD, TIMER_PRD, SCL_LP, and SCL_HP where:
This value is determined by replacing the known variables in Equation 5 and solving for TIMER_PRD.
The I2C clock period is calculated as in Equation 5:
For example:
CLK_PRD = 12.5 ns
TIMER_PRD = 39
SCL_LP = 6
SCL_HP = 4
yields a SCL frequency of:
1/SCL_PERIOD = 100 kHz
Table 7-2 gives examples of the timer periods to generate standard and fast mode SCL frequencies based on the fixed 80-MHz system clock frequency.
| System Clock | Timer Period | Standard Mode | Timer Period | Fast Mode | |
|---|---|---|---|---|---|
| 80 MHz | 0x27 | 100 kbps | 0x09 | 400 kbps |