ZiLOG Z80-RIO Operating System User's Manual page 137

(IY+lO)
(IY+ll)
Completion code (1 byte) - indicates
when the operation is complete.
This byte is set to zero when the
call is made. Bit 7 is set when the
operation is complete. Bit 6 is set
if an error occurred. The remainder
of the byte will contain a code
indicating the nature of the difficulty
or error. A normal completion will
thus contain a code of 'SO'.
Supplemental parameter information -
some requests require special
information which does not fit into
the general structure of the parameter
vector. This information is supplied
by the supplemental parameter vector.
If two bytes or less (e.g., a disk
address), it is normally put here.
Otherwise an address pointer to an
area containing the information is
placed here.
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