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→Read-only modes
===Read-only modes===
Some applications require to implement write protection schemes in order to inhibit write operations on non-volatile memory. DUL provides two signals to accomplish this:
* SET_WP#: this signal is directly connected to the NAND flash controller. When low, ontroller disables any write operations on NAND flashare disabled by controller. This signal is provided to implement write protect mechanism like the switch of consumer USB pen drive. If not used, it must be left open.
* EXT_FWP#: this signal is connected directly to the WPn pin of NAND flash device. Two options are available:
** by default, it is output only and is used to inform carrier board logic about the write protection enabling decided determined by controller. This can be used, for example, to implement warning signalling for the user.
** on request it can be provided as bidirectional open-drain pin. In this case, beside the output function described previously, it allows carrier board logic to inhibit NAND flash write operations directly. For example system integrator could imagine a scenario where a hardware watchdog - that monitors host processor connected to DUL - acts on this pin disabling write operations in case processor hangs.