Context: As per #378, the previously used SN74LVC4245A was replaced with SN74LXCH8T245.
SN74LXCH8T245 has in-built 'bus-hold' functionality which causes it to remember the previous logic state even if the device is powered off. I don't think this is ideal, firstly because the datasheet explicitly states not to use pulldown/pullup resistors on the inputs (see below). mega-mcu-144 module (v7.0) has 10k pulldown resistors on the input pins to pull them low when pin floats/when the device is off/disconnected.
Secondly, even if the resistors are removed/not placed, remembering the previous state could cause an output to unintentionally go high e.g. after a reset or power loss, the level shifter will actively lock the output in its last known state instead of dropping to 0V. And if it is logic high, the ignition coil IGBT gate will be continuously charged.
I am not entirely sure that this is a concern, but perhaps replacing with the non-H version (SN74LXC8T245) makes more sense instead anyways.
Context: As per #378, the previously used SN74LVC4245A was replaced with SN74LXCH8T245.
SN74LXCH8T245 has in-built 'bus-hold' functionality which causes it to remember the previous logic state even if the device is powered off. I don't think this is ideal, firstly because the datasheet explicitly states not to use pulldown/pullup resistors on the inputs (see below).
mega-mcu-144module (v7.0) has 10k pulldown resistors on the input pins to pull them low when pin floats/when the device is off/disconnected.Secondly, even if the resistors are removed/not placed, remembering the previous state could cause an output to unintentionally go high e.g. after a reset or power loss, the level shifter will actively lock the output in its last known state instead of dropping to 0V. And if it is logic high, the ignition coil IGBT gate will be continuously charged.
I am not entirely sure that this is a concern, but perhaps replacing with the non-H version (SN74LXC8T245) makes more sense instead anyways.