ARM Technical Support Knowledge Articles

I'm not implementing an external coprocessor. How should I tie off the interface?

Applies to: ARM920/922T, ARM926EJ-S, ARM940T, ARM946E-S, ARM966E-S, ARM9TDMI


Make sure that the coprocessor handshake signals (CHSD and CHSE, or CHSDE and CHSEX) are tied off correctly to 2'b10 (ABSENT).

Failing to do this will cause your design to behave in an unpredictable way or hang when a Coprocessor Instruction is executed (including instructions for the Control coprocessor, CP15).

All other inputs on the CP interface should be tied low.

See also:

Article last edited on: 2008-09-09 15:47:37

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