By a process of elimination (There just ain't anything else in the unit that it could be - the tiny number of other chips involved have all been identified, leaving this one as the only possibility) a chip labeled
"ZX1258A
230803" <--- I expect this is most likely a date code
seems to be the MCU on the "brain-board" of a chinese white-label split-phase inverter. (When fed roughly 150 Amps of 48VDC, the unit outputs "L1/L2/N" with L1-N and L2-N being two legs of 60Hz 120VAC@just under 30Amps each, with each leg 180 degrees out of phase with the other for "regular USA-style wall-socket power", and L1-L2 giving 240VAC@just under 60Amps for heavy loads like well pumps, clothes dryers, water heaters, etc) The unit is intended to have the output be wired straight into a panel as a direct replacement for the normal L1/L2/N of a standard residential power company hookup - just not as "beefy". (a normal power company drop is typically going to be good for around 100-200 amps, this unit tops out around 60 amps)
So far, I can find exactly NOTHING about this chip through every search engine, AI, or forum I've tried consulting. Haven't come up with even a manufacturer name, never mind datasheets, programming info, etc. The closest I've come is an AI query that suggested it might be made by Zhong Xing Mfg out of China as a ""best guess", but on exploring the possibility, they turn out to be an outfit that seems to be primarily concerned with making specialty carburetors (and rebuild kits for same) to go on racing motorcycle engines.
Anybody encountered this beast or know anything about it? Even hints ("It's a fancied-up/dumbed-down 8051 variant made by ______.") could help point me in the right direction to find the info I need.
The chip body is roughly 7-8mm (close enough to 1/4 inch) square by about 2-3mm (about 1/8-3/16 inch) thick, looks and feels like black plastic with a semi-matte surface, and has 12 fine-pitch SMD legs per side. No visible markings other than what's already been given, no logo of any kind, no heatsink plate (unless it's hidden on the bottom of the chip) - just a roughly 1/4 inch plain black plastic square with 48 legs that has "ZX1258A" and "230803" printed on it in white.
In case it's of any help, and since they say a picture is worth a thousand words...

Any help out there?
"ZX1258A
230803" <--- I expect this is most likely a date code
seems to be the MCU on the "brain-board" of a chinese white-label split-phase inverter. (When fed roughly 150 Amps of 48VDC, the unit outputs "L1/L2/N" with L1-N and L2-N being two legs of 60Hz 120VAC@just under 30Amps each, with each leg 180 degrees out of phase with the other for "regular USA-style wall-socket power", and L1-L2 giving 240VAC@just under 60Amps for heavy loads like well pumps, clothes dryers, water heaters, etc) The unit is intended to have the output be wired straight into a panel as a direct replacement for the normal L1/L2/N of a standard residential power company hookup - just not as "beefy". (a normal power company drop is typically going to be good for around 100-200 amps, this unit tops out around 60 amps)
So far, I can find exactly NOTHING about this chip through every search engine, AI, or forum I've tried consulting. Haven't come up with even a manufacturer name, never mind datasheets, programming info, etc. The closest I've come is an AI query that suggested it might be made by Zhong Xing Mfg out of China as a ""best guess", but on exploring the possibility, they turn out to be an outfit that seems to be primarily concerned with making specialty carburetors (and rebuild kits for same) to go on racing motorcycle engines.
Anybody encountered this beast or know anything about it? Even hints ("It's a fancied-up/dumbed-down 8051 variant made by ______.") could help point me in the right direction to find the info I need.
The chip body is roughly 7-8mm (close enough to 1/4 inch) square by about 2-3mm (about 1/8-3/16 inch) thick, looks and feels like black plastic with a semi-matte surface, and has 12 fine-pitch SMD legs per side. No visible markings other than what's already been given, no logo of any kind, no heatsink plate (unless it's hidden on the bottom of the chip) - just a roughly 1/4 inch plain black plastic square with 48 legs that has "ZX1258A" and "230803" printed on it in white.
In case it's of any help, and since they say a picture is worth a thousand words...

Any help out there?