GN_M16, 16bit unsigned multiplication

RST 20H, DEFW $7209

IN:

     HL = multiplicand
     DE = multiplier

     Fc = 0
     HL = product, least significant 16bits - no warning is given of
     overflow.

     A.BCDE../IXIY same
     .F....HL/.... different

Bugs:
 

Related calls:

GN_D16, 16bit unsigned division
GN_D24, 24bit unsigned division
GN_Gdn, convert an ASCII string to a binary number
GN_M24, 24bit unsigned multiplication
GN_Pdn, write number as decimal ASCII string