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NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
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Revision V1.30
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5.1.5 Bus Interface Unit
The ARM926EJ-S Bus Interface Unit (BIU) arbitrates and schedules AHB requests. The BIU
contains separate masters for both instruction and data access enabling complete AHB system
flexibility. Each master is a fully compliant AHB bus master and implements the master functions
as defined in the AMBA Specification (Rev 2.0).
To increase system performance, write buffers are used to prevent AHB writes stalling the
ARM926EJ-S system.
5.1.6 Power Management
The ARM926EJ-S processor can be put into a low-power state by the wait for interrupt instruction:
MCR p15, 0, <Rd>, c7, c0, 4
This instruction switches the ARM926EJ-S processor into a low-power state until either an
interrupt (IRQ or FIQ) or a debug request occurs.
In wait for interrupt mode, all internal ARM926EJ-S clocks are stopped. The switch into the low-
power state is delayed until all write buffers have been drained, and the ARM926EJ-S memory
system is in a quiescent state.