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Pin 31 (UART_TXD0) Transmit data output on port P21 of R-IN32M3-EC (URTJ0TTXD).
Pin 32 (UART_RTS0) optional Ready To Send on port P43 of R-IN32M3-EC.
Pin 33 (GND) optional Ground
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Pin 35 (UART_TXD1) Transmit data output on port P31 of R-IN32M3-EC (URTJ1TTXD).
Pin 36 (UART_RTS1) optional Ready To Send on port P74 of R-IN32M3-EC.