GN_Gmt, get (read) machine system time in internal format

RST 20H, DEFW $1A09

IN:

     C = Least significant byte of system date from last GN_Gmd call.
     (optional)
     DE = 0, not allowed.
     DE = 1, not allowed.
     DE = 2, return system time in ABC.
     DE > 255, pointer to write system date at (DE)

     Fz = 0, C(in) is inconsistent with input parameter.
     Fz = 1, C(in) is consistent with time read
     DE, DE = DE(in) if DE < 255, else DE = DE(in) + 3
     ABC, ABC = ABC(in) if DE > 255 else contains the result

     ......HL/IXIY same
     AFBCDE../.... different

A = high byte, C = low byte. If result stored at (DE) then (DE) = low byte, (DE+2) = high byte (Z80 convention).

Related calls:

GN_Gtm, convert an ASCII string to a time in internal format
GN_Msc, miscellaeneous time operations
GN_Pmt, put (set) machine time
GN_Ptm, write internal time as ASCII string
GN_Sdo, send date and time to standard output
OS_Dly, delay a given period