Functional Description
ARM DDI 0388I
Copyright © 2008-2012 ARM. All rights reserved.
2-6
ID073015
Non-Confidential
2.3
Clocking and resets
This section describes the clocks and resets of the processor in:
•
•
•
Dynamic high level clock gating
2.3.1
Synchronous clocking
The Cortex-A9 uniprocessor has one functional clock input,
CLK
.
The Cortex-A9 uniprocessor does not have any asynchronous interfaces. All the bus interfaces
and the interrupt signals must be synchronous with reference to
CLK
.
The AXI bus clock domain can be run at n:1 (AXI: processor ratio to
CLK
) using the
ACLKEN
signal.
ACKLENM0
used with a 3:1 clock ratio between
CLK
and
ACLK
in a Cortex-A9 uniprocessor.
Figure 2-3
ACLKENM0
used with a 3:1 clock ratio
The master port, Master0, changes the AXI outputs only on the
CLK
rising edge when
ACLKENM0
is HIGH.
2.3.2
Reset
The Cortex-A9 processor has the following reset inputs:
nCPURESET
The
nCPURESET
signal is the main Cortex-A9 processor reset. It
initializes the Cortex-A9 processor logic and the FPU logic including the
FPU register file when the MPE or FPU option is present.
nNEONRESET
The
nNEONRESET
signal is the reset that controls the NEON SIMD
independently of the main Cortex-A9 processor reset.
nDBGRESET
The
nDBGRESET
signal is the reset that initializes the debug logic. See
All of these are active-LOW signals.
Address1
Address2
Address3
CLK
ACLK
ACLKENM0
ARRDRM0
Address0