OS_Ht, hardware time manipulation

Register parameters

RST 20H, DEFW $F206

IN:
     A = HT_RES ($01), reset hardware timer
     A = HT_RD ($02), read hardware timer
     HL = pointer to a 5 byte buffer

OUT:     -

Registers changed after return:
     A.BCDEHL/IXIY same
     .F....../.... different

IN:  A = HT_MDT ($03), read monthy/date/time address
OUT: Fc = 0
     BHL = month, date, time address

Registers changed after return:
     ...CDE../IXIY same
     AFB...HL/.... different

Notes

Internal operating system usage.