I think there is a problem with the syntax in this extract from the TMS320C5504 DSP System User's Guide, SPRUGH6A.pdf, section 1.7.3.1.
"Before modifying the values of the external bus selection register, you must clock gate all affected
peripherals through the Peripheral Clock Gating Control Register"
Could this be worded more clearly? What must happen before modifying EBSR?