Sharing SPI bus

[Silenus]

I am designing a MCU embedded system using an AVR and I need the SPI bus for a wifi module. However, I also need this bus to program the chip via ICSP headers. Will having the wifi module on the same bus cause any ill effects when I program my chip? or should I go for a MCU that has two SPI buses?

[0xdeadbeef]

SPI is a master slave bus where usually the MCU is the master. A slave must not do anything on the bus if its chip select is not active. So given the CS line is deactivated during reprogramming the WiFi module should not be an issue.

[LukeW]

In this case it can be worthwhile to put a pullup on the peripheral device !CS line, to stop it going low or getting into a funny state during microcontroller programming.