Are isolation resistors necessary for SPI devices on the same bus as the ISP if the device uses CPOL = 1 and CPHA = 1?
ckalas
Isolation resistors necessary for SPI devices with opposite phase/polarity?
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js 
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I don't think I really understand what you are asking but anyway: 
The ISP header must be connected directly to the SPI pins
Resistors are likely to slow down communications, not necessary if each slave device has a CS pin and you use a pullup or pulldown on the pin depending on polarity.
Unless you have the chip select enabled on more than 1 devise (VERY BAD IDEA) you can do anything you want with the polarity as only the device enabled talks to the SPI.
Make sure you change the setting of the SPI depending on clock and phase polarity expected by the slave device you are addressing.
stevech ckalas wrote:
I'd think not. When the slave select (SS) is false the slave device shall ignore the clock and data lines and NOT assert a logic level on MISO.
Are isolation resistors necessary for SPI devices on the same bus as the ISP if the device uses CPOL = 1 and CPHA = 1?