May I know the MCP23S09 does not have an address pin means that I need to control another io expander with a new SPI Module?

 

No, you can decide which one you are addressing by using the CS line. (Though if you had a spare IO line to connect to CS, why would you need an IO expander?)

 

No, you can decide which one you are addressing by using the CS line. (Though if you had a spare IO line to connect to CS, why would you need an IO expander?)

thanks, I forget about CS then may I know what is the use of the address pin in MCP23S17 the reason I need to use the IO expander as I need to control the 100++ relay switch on and off

 

You can use the address pins to address multiple MCP23S17 on the same CS line. This can be enabled in the IOCON register.

 

You can use the address pins to address multiple MCP23S17 on the same CS line. This can be enabled in the IOCON register.

Does any platform have a sample code to interface this mcp io expander?

 

You can also use a 74HC138 to generate eight CS signals from 3 outputs (or a 74HC154 to generate 16 from 4), but watch the maximum fan-out from the MCU. You might need to buffer MISO and SCK.
Alternatively, Microchip make some expanders with I2C interfaces.