SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
Тo obtain desired base frequency of SCL signal for SDR/HDR I3C messaging (I3C_FREQ) the I3C_PRESCL_CTRL0[9-0] I3C bit-field should be programmed with value defined by the following equation:
Programming the prescalers must be performed prior to enabling I3C Master controller with I3C_CTRL[31] DEV_EN bit in the control register.
In all timing schemes, the base frequency resulting from prescalers corresponds directly to the duration of the high level of the SCL line which takes always 50% of the base period. Depending on various conditions, the duration of low level is extended beyond the base period as necessary.
There is a specific relationship between SCL frequency and system clock frequency, which requires system clock to have a multiple of four cycles per each SCL period. Thus the selection of system clock frequency must be done with caution, since only specific frequencies will allow configuring SCL to fit into desired bandwidth.
Table 12-332 presents achievable SCL frequencies for exemplary set of system clock frequency values.
I3C0_SCLK / MCU_I3C0_SCLK frequency | I3C_PRESCL_CTRL0[9-0] I3C | Actual frequencies |
---|---|---|
100 MHz | 0x2 | 8.33 MHz |
133 MHz | 0x3 | 8.313 MHz |
166 MHz | 0x3 | 10.375 MHz |
200 MHz | 0x4 | 10 MHz |