How much maximum LPUART2 Baudrate can be set for stable communication on FS32K144
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Hi @bryan_hong,
The LPUART functional clock can be set up to the BUS_CLK freq, which is 56MHz in HSRUN and 48MHz in RUN.
Baudrate = LPUART functional clock / SBR (min 1) * OSR (min 4)
That means the baudrate can be even 14 MHz in HSRUN.
This is rather limited by the AC electrical specification of the IOs and by the electrical characteristics of the bus.
S32K1xx, Datasheet, rev14
5.1 AC electrical characteristics
5.2 General AC specifications
Table 23. AC electrical specifications at 5 V Range for S32K1xx series
Regards,
Daniel
thanks Daniel for quick updates.
How to get the 14Mhz ?
48/1*(4+1) = 9.6
Theoretically in HSRUN.
56 MHz / (1 * (3 + 1)) = 14 MHz
BR, Daniel
thanks for update
Not theoretically, can this be enabled stable in practice?
Is there a use case for max baudrate that was actually used?
Bryan
Hi @bryan_hong,
Why do you need this baudrate? I'm not aware of such a use case.
With this configuration, there would be oversampling rates of 4x.
The baudrate (14 MHz) would have 71.4ns period.
There are no GPIO-HD (PORTn_PCR[DSE] = 1) LPUART pins, only GPIO (PORTn_PCR[DSE] = 0), refer to S32K144_IO_Signal_Description_Input_Multiplexing.xlsx
At 200pF bus capacitance, the slew rate of the pins can be up to 54.8ns / 5V (Rise time), 59.7ns / 5V (Fall time).
As you can see, it depends on the electrical characteristics of the bus.
Regards,
Daniel
Hi @bryan_hong,
The LPUART functional clock can be set up to the BUS_CLK freq, which is 56MHz in HSRUN and 48MHz in RUN.
Baudrate = LPUART functional clock / SBR (min 1) * OSR (min 4)
That means the baudrate can be even 14 MHz in HSRUN.
This is rather limited by the AC electrical specification of the IOs and by the electrical characteristics of the bus.
S32K1xx, Datasheet, rev14
5.1 AC electrical characteristics
5.2 General AC specifications
Table 23. AC electrical specifications at 5 V Range for S32K1xx series
Regards,
Daniel