Quote:
Is this the same op-amp that senses absolute low voltage and tells the Empeg to write to flash and shut off?


Rob's explained the hardware side; here's how it works in the software:

Every now and then, the player writes the contents of the flash area to kernel space. Rather than write it to flash immediately (which would wear out the flash too quickly), it's cached in kernel space.

When the op-amp sees the voltage drop, it signals the CPU, which prompts the kernel to write this cached data into the real flash device. There's usually enough juice in the on-board capacitors that this succeeds before the power drops out completely. This is why the display is turned off at this point -- it leaves more runtime from the juice in the caps.

In case it doesn't succeed, the block written to the flash has a checksum in it. This means that when the player starts up, it can avoid loading a half-written flash block.

The player cycles through several flash blocks, which means that it can always get a 'last known good' block, even if the last one was corrupt.

If, after flushing to flash memory, the power comes back, and the player is still running, then the player displays the low battery icon. Thus, it's not actually telling you that the voltage is low at that point. It's telling you that the voltage dropped out just now, and you should maybe check your installation.

It doesn't actually tell the empeg to 'shut off'. The power going away is all the 'off' that the player needs.
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-- roger