I'm more interested in how it sends power on/off pulses. With the Carnetix, if you turn on the car, and then turn it off during the computer's startup time, it will not send the shutdown pulse until the startup time period has passed (so it has time to start up properly, so the shutdown pulse will actually get it to shut off). Does the M1-ATX also do this?
This does not apply to the M1-ATX, since the M1-ATX is a true PSU and listenes (most of the time) to PSON signals. We do have some safety tricks implemented around simimlar issues, but again, this particular case will not apply.
Originally posted by Change
Does anyone know if the M1-ATX has a bootup lockout state, like the Carnetix regulators?
After reading Andrewb's response, I deleted my previous post in this thread thinking I had given errant information.
Having rethought it though, I now stand behind my original response. The first two versions of the M1-ATX firmware do not appear to gracefully handle this scenario.
PSON# is low and the PSU is already on. If the ignition goes low for longer than the off delay, the PSU will generate the power button pulse. The PSU does not know (or assume via a timer) that the OS is still booting. Since the booting OS will never respond to the pulse, from the PSU point of view it will look like the system has failed to shutdown. In that case, the PSU will still bring the system down forcefully once the HARDOFF timer expires or when the battery voltage drops below 11V; whichever comes first, or not at all if the ignition is turned back on.
The state of PSON alone does not give the PSU enough information to handle this scenario (and related scenarios) gracefully in all cases. Some sort of timer is needed to maximize the chance (though not guarantee) that the system shutsdown gracefully when possible.