Warning: This is all based on what I have inferred through interacting with the Epever Tracer 3210AN {0: b'EPsolar Tech co., Ltd', 1: b'TriRon3210', 2: b'V01.55+V01.22'}. Please treat this repository as informational only and test carefully before assuming any of this will work with your device.
The undocumented Epever 0x43 (67) modbus command is similar to the regular read register command (0x4) except that it allows reading discontinguous registers.
The request format is the same - two big-endian short integers indicating the starting register address and the number of registers to retrieve;
+---------+--------------+------------------------+----------------+-----+
| | | | | |
| unit_id | command=0x43 | start_register_address | register_count | crc |