SMC Networks AHB SRAM/NOR, PL241 manual an active output domaincactive

Models: AHB SRAM/NOR PL241

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an active output

Functional Overview

an active output

<domain>_cactive

Where:

<domain> is ahb or smc.

Figure 2-7explains the protocol for the interface by showing a request to enter low-power mode.

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KFON

DKEBFV\VUHT

DKEBFV\VDFN

DKEBFDFWLYH

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 2-8shows the AHB domain denying a low-power request.

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KFON

DKEBFV\VUHT

DKEBFV\VDFN

DKEBFDFWLYH

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.

ARM DDI 0389B

Copyright © 2006 ARM Limited. All rights reserved.

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SMC Networks AHB SRAM/NOR, PL241 manual an active output domaincactive