Interrupts

Interrupts

The WonderSwan features fourteen different interrupts:

• CPU interrupts - six provided by the V30MZ CPU ($00-$05),
• Hardware interrupts - eight provided by the SoC's hardware ($00-$07, or $08-$0F, or $10-$1F, or ... $F8-$FF - controlled by an offset V):
  • Level - will be constantly requested while the prerequisite condition is true; interruption can only be prevented by resolving the condition or disabling the interrupt;
  • Edge - will only be requested when the prerequisite condition becomes true; acknowledging the interrupt prevents further interruption.

The user can additionally define and use any of the 256 interrupt vectors in their own code.

List of WonderSwan interrupts

Source	Type	Index	Description
CPU	N/A	$00	DIV or IDIV instruction divide error (division by zero or result overflow)
		$01	Single-step (T flag)
		$02	NMI (non-maskable interrupt)
		$03	INT 3 opcode
		$04	INTO opcode (if V = 1)
		$05	BOUND opcode (if index out of bounds)
Hardware	Level	V + 0	UART Send Ready
	Edge	V + 1	Key Pressed
	Level	V + 2	Cartridge IRQ
		V + 3	UART Receive Ready
	Edge	V + 4	Display Interrupt Line Match
		V + 5	Vertical Blank Timer
		V + 6	Display Vertical Blank
		V + 7	Horizontal Blank Timer

I/O ports

Interrupt Vector Offset ($B0 write)

7  bit  0
---- ----
VVVV V...
|||| |
++++-+---- Interrupt vector offset

Interrupt Vector Request ($B0 read)

7  bit  0
---- ----
vvvv vvvv
|||| ||||
++++-++++- Interrupt vector requested
           from the CPU.

• Bits 7 .. 3 of this will always equal the user-provided vector offset.
• Bits 2 .. 0 of this will always equal the highest set bit index of Interrupt Status; if all bits in Interrupt Status are clear, they will equal 0.

Interrupt Enable ($B2)

7  bit  0
---- ----
iiii iiii
|||| ||||
++++-++++- Hardware interrupt to enable
           (acts as a mask)

Interrupt Status ($B4 read)

7  bit  0
---- ----
iiii iiii
|||| ||||
++++-++++- 1 if interrupt requested

Interrupt Acknowledge ($B6 write)

7  bit  0
---- ----
iiii iiii
|||| ||||
++++-++++- Write 1 to clear interrupt request

Interrupt NMI Control ($B7)

7  bit  0
---- ----
...b ....
   |
   +----- Enable NMI on low battery detection