HT46R064D/065D/066D
Enhanced A/D Type 8-Bit OTP MCU with LED Driver
Once an interrupt subroutine is serviced, all the other interrupts will be blocked, as the EMI bit will be
cleared automatically. This will prevent any further interrupt nesting from occurring. However, if other
interrupt requests occur during this interval, although the interrupt will not be immediately serviced,
the request flag will still be recorded. If an interrupt requires immediate servicing while the program is
already in another interrupt service routine, the EMI bit should be set after entering the routine, to
allow interrupt nesting. If the stack is full, the interrupt request will not be acknowledged, even if the
related interrupt is enabled, until the Stack Pointer is decremented. If immediate service is desired, the
stack must be prevented from becoming full.
When an interrupt request is generated it takes 2 or 3 instruction cycle before the program jumps to the
interrupt vector. If the device is in the Sleep Mode and is woken up by an interrupt request then it will
take 3 cycles before the program jumps to the interrupt vector.
Main
Program
Interrupt Request or
Interrupt Flag Set by Instruction
N
Enable Bit Set ?
Y
Main
Automatically Disable Interrupt
Program
Clear EMI & Request Flag
Wait for 2 ~ 3 Instruction Cycles
ISR Entry
RETI
(it will set EMI automatically)
Interrupt Flow
Rev. 1.00
66
January 12, 2011
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
