
	Interrupt Processing Sequence


The interrupt processing sequence is initiated as the direct result of hard-
vare Abort, Interrupt Request, Non-Maskable Interrupt, or Reset inputs.
The interrupt sequence can also be initiated as a result of the Break or
Co-Processor instructions within the software. The following listings
describe the function of each cycle in the interrupt processing sequence:


Hardware Interrupt /ABORT, /IRQ, /NMI, /RES Inputs

Cycle No.
 E = 0 E = 1 Address  Data   R/W  SYNC VDA VPA  VP Description

   1     1    PC        X     1    1    1   1   1  Internal Operation
   2     2    PC        X     1    0    0   0   1  Internal Operation
   3    [1]    S       PB     0    0    1   0   1  Write PB to Stack, S-1ÑS
   4     3     S     PCH [2] 0[3]  0    1   0   1  Write PCH to Stack, S-1ÑS
   5     4     S     PCL 12] 0[3]  0    1   0   1  Write PCL to Stack, S-1ÑS
   6     5     S      P [4]  0[3]  0    1   0   1  Write P to Stack, S-1ÑS
   7     6    VL      (VL)    1    0    1   0   0  Read Vector Low Byte,
							 0->PD, 1->P1, OO->PB
   8     7    VH      (VH)    1    0    1   0   0  Read Vector High 8yte


Software Interrupt - BRK, COP Instructions

Cycle No.
 E = 0 E = 1 Address  Data   R/W  SYNC VDA VPA  VP Description
   1     1   PC-2       X     1    1    1   1   1  Opcode
   2     2   PC-1       X     1    0    0   1   1  Signature
   3    111    S       PB     0    0    1   0   1  Write PB to Stack, S-1ÑS
   4     3     S       PCH    0    0    1   0   1  Write PCH to Stack, S-1 - S
   5     4     S       PCL    0    0    1   0   1  Write PCL to Stack, S-1ÑS
   6     5     S        P     0    0    1   0   1  Write P to Stack, S-1ÑS
   7     6    VL      (VL)    1    0    1   0   0  Read Vector Low Byte,
							 0ÑPo, 1ÑPl, 00ÑPB
   8     7    VH      (VH)    1    0    1   0   0  Read Vector High Byte

Notes:
	[1] Delete this cycle in Emulation mode.
	[2] Abort writes address of aborted opcode.
	[3] R/W remains in the high state during Reset.
	[4] In Emulation mode, bit 4 written to stack is changed to 0.



	Table 3. Vector Locations

				Emulation   Native	Priority
	Name	Source		(E = 1)	    (E = 0)	Level

	ABORT	Hardware	00FFF8,9    00FFE8,9	 2
	BRK	Software	00FFFE,F    00FFE6,7	N/A
	COP	Software	00FFF4,5    00FFE4,5	N/A
	IRQ	Hardware	00FFFE,F    00FFEE,F	 4
	NMI	Hardware	00FFFA,B    00FFEA,B	 3
	RES	Hardware	00FFFC.D    00FFFC,D	 1

