OS_Bhl, copy bytes from extended address

RST 20H, DEFW $DC06

IN:

     C = number of bytes to copy (0 to 255)
     BHL = extended source pointer
     DE = local destination pointer

     Fc = 0 always

     A.BCDEHL/IXIY same
     .F....../.... different

Bugs:

The call does not work if the source pointer defines memory in segments 2 or 3.

GN_Cme, compare null-terminated strings, one local, one extended
GN_Rbe, read byte at extended address
GN_Wbe, write byte at extended address
OS_Bde, copy bytes to extended address