SMC Networks PL241, AHB SRAM/NOR manual Direct commands, Device pin mechanism, Software mechanism

Models: AHB SRAM/NOR PL241

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Direct commands

Functional Overview

Direct commands

The SMC enables code to be executed from the memory while simultaneously, from the software perspective, moving the same chip to a different operating mode. This is achieved by synchronizing the update of the chip configuration registers from the holding registers with the dispatch of the memory configuration register write.

The SMC provides two mechanisms for simultaneously updating the controller and memory configuration registers.

Device pin mechanism

For memories that use an input pin to indicate that a write is intended for the configuration register, for example in some PSRAM devices, the write mechanism can be done through the APB direct command register. Figure 2-12 on page 2-25shows the sequence of events.

Software mechanism

For memories that require a sequence of read and write commands, for example, most NOR Flash devices use the SMC interface, with the write data bus indicating when the last transfer has completed and when it is safe for the SMC to update the chip configuration registers. Figure 2-13 on page 2-26shows the sequence of events.

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Copyright © 2006 ARM Limited. All rights reserved.

ARM DDI 0389B

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SMC Networks PL241, AHB SRAM/NOR manual Direct commands, Device pin mechanism, Software mechanism