ARM Technical Support Knowledge Articles

General: The specification recommends that only 16 wait states are used. What should you do if more than 16 cycles are needed?

Applies to: AHB

Answer

For some slaves it is acceptable to insert more than 16 wait states. For example, a serial boot ROM which is only ever accessed at initial power up could insert a larger number of wait states and it would not affect the calculation of the system performance and latency once system power up has been completed.

For other slaves a number of options exist. A SPLIT or RETRY response could be used to indicate that the slave is not yet able to perform the requested data transfer, or the slave could be accessed either in response to interrupts or after polling a status register, in either case indicating that the slave is now able to respond in an acceptable number of cycles.

See also:

Article last edited on: 2014-02-06 14:32:54

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