I have never used the DEC and HEX qualifiers in the HSERIN command.

If I issue the command

HSERIN [HEX X]

Does that convert a received "A2" received as two ASCII characters into
binary %10100010 and put that in the variable X?

Or - does it just filter out any ASCII character that isn't in the range of "0" to "9" or "A" to "F" and save a "0" as 0x30 to X?

Just what does it do?