Hi Yasumasa Ogawa,
I am not sure if serial connection of two PCA9509 is possible. The PCA9509 was not intended for such connection. Only way possible could be to connect the B ports together and I2C ICs on the A ports.
Could you please provide more details about your application? Perhaps we can offer you a better component for your application.
With Best Regards,
Jozef
To Jozef
thank you for your answer.
Insert the board into the subrack.
I2C communication between boards.
Since it passes through the backboard, I am thinking of mounting an I2C repeater on each board.
Best Regards