Sanyo MBC-550 Series User Manual page 259

is masked, response may be delayed
If IR2 or IR3
because fetching results in polling by software.
Within BIOS, only the I/O routine related to the floppy
disk is disabled. No interrupts are accepted while
this routine being executed.
Of IRO to IR7, interrupts other than IR1 k to IR3 and
IR5 can be used by a transient program.
To use interrupts, write the segment and offset the
interrupt servicing routine and reset the corresponding
IMR bits. If the program has terminated, restore the
rewritten vector, set the reset IMR bits, then return
control to DOS. IF the vector and the IMR are not
restored, an overrun results.
NOTE: to use interrupt, master the operations of 8088
and 8259A beforehand.
5—18