REF="#Reg4200">register $4200</A> are set, then as soon as the H/V
counter timer becomes the count value set in <A HREF="#Reg4207">registers
$4207 to $420A</A>, then an IRQ will be "applied" (unless the CPU interrupt
flag is enabled.&nbsp; If this is the case, then the interrupt will be
called as soon as the flag is cleared.)&nbsp; The IRQ routine must immediately
use SEI to prevent recursive calling, then read from this register to "un-apply"
the interrupt.&nbsp; The first read will return 1 in the i bit, 