1 Reply Latest reply on Aug 7, 2019 7:08 PM by TakashiM_61

    UART max Baud rate of FM3 CY9B110T Series

    HaSh_1328096

      Hi,

       

      FM3 CY9B110T Series.

      It seems like UART max baud rate is 8MHz, Why isn't it 14.4 MHz?

       

      In the document 'FM3 Peripheral Manual Communication Macro Part (TRM)',

      following formula is shown.

       

      V = φ/ b - 1

       

        V : Reload value  

        b : Baud rate

           φ: Bus clock frequency or external clock frequency

       

      CY9B110T Series APB2 Bus clock is max 72MHz and  V is min 4.

      Even considering the allowable baud rate range for reception,

      Maximum baud rate is..

       

      b = φ/( V + 1 ) = 72 Mhz  / ( 4+1 )  = 14.4Mhz  ( baud rate max )

       

      However, in the data sheet it is 8 MHz.

      (※Document History 03/09/2017 Added the Baud rate spec in “12.4.10 CSIO/UART Timing”)

       

      ■CY9B110T Series, 32-bit Arm® Cortex®-M3 based Microcontroller Datasheet

       https://www.cypress.com/file/252801/download

      ■32-bit Microcontroller FM3 Peripheral Manual Communication Macro Part

       https://www.cypress.com/file/211101/download

       

      Why is this?

      Is it because the specification of MFT needs 8 clocks

      for setting the interrupt flag by checking the reception idle status?

       

      Is there any other reason?

       

      Best regards.

      Shimoda