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Functional Overview
ARM DDI 0389B
Copyright © 2006 ARM Limited. All rights reserved.
2-13
an active output
<domain>_cactive
Where:
<domain> is ahb or smc.
Figure 2-7 explains the protocol for the interface by showing a request to enter
low-power mode.
Figure 2-7 Request to enter low-power mode
The memory controller receives a request to enter low-power mode, indicated by
<domain>_csysreq
being driven LOW by the system clock controller, as shown at T1.
The memory controller then has the chance to perform any required operations to
prepare for the clock to be switched off. The memory controller acknowledges the
request by asserting
<domain>_csysack
LOW, as shown at T2. At this point the
<domain>_cactive
signal is used to indicate whether the request has been accepted or
denied. If the request is accepted,
<domain>_cactive
is LOW, as shown in Figure 2-7.
If the request is denied,
<domain>_cactive
is HIGH. If the request is accepted, then the
clock to that domain can be switched off. The peripheral is brought out of low-power
state by restarting the clock and driving
<domain>_csysreq
HIGH, as shown at T4. The
memory controller completes the handshake by driving
<domain>_csysack
HIGH, as
shown at T5. Figure 2-8 shows the AHB domain denying a low-power request.
Figure 2-8 AHB domain denying a low-power request
When
ahb_csysack
is asserted LOW, the
ahb_cactive
signal is HIGH, as shown at T3,
indicating the AHB domain is busy and the clock cannot be switched off. The
handshake must be completed.
KFON
DKEBFV\VUHT
DKEBFV\VDFN
DKEBFDFWLYH
7
7
7
7
7
KFON
DKEBFV\VUHT
DKEBFV\VDFN
DKEBFDFWLYH
7
7
7
7
Содержание PrimeCell PL241
Страница 20: ...Introduction 1 6 Copyright 2006 ARM Limited All rights reserved ARM DDI 0389B ...
Страница 60: ...Functional Overview 2 40 Copyright 2006 ARM Limited All rights reserved ARM DDI 0389B ...
Страница 94: ...Device Driver Requirements 5 6 Copyright 2006 ARM Limited All rights reserved ARM DDI 0389B ...
Страница 104: ...Signal Descriptions A 10 Copyright 2006 ARM Limited All rights reserved ARM DDI 0389B ...
Страница 110: ...Glossary Glossary 6 Copyright 2006 ARM Limited All rights reserved ARM DDI 0389B ...