Interrupts: Difference between revisions

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== Interrupts ==
The WonderSwan features fourteen different interrupts:
The WonderSwan features fourteen different interrupts:


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


The user can additionally define and use any of the 256 interrupt vectors in their own code.
Interrupt requests happen when the condition is true and the interrupt is enabled. Note that edge interrupts are only requested once; level interrupts are requested constantly, making acknowledgements ineffective until the condition is cleared or the interrupt is disabled. However, neither disabling an interrupt nor satisfying the condition clears the acknowledgement bit.
 
The user can additionally make use of all 256 available interrupt vectors in their own code.


{| class="wikitable"
{| class="wikitable"
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== I/O ports ==
== I/O ports ==


=== Interrupt Vector ===
{{Anchor|Interrupt Vector Offset}}
=== Interrupt Vector Offset ($B0 write) ===


<pre>
<pre>
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---- ----
---- ----
VVVV V...
VVVV V...
|||| |
++++-+---- Interrupt vector offset
</pre>
{{Anchor|Interrupt Vector Request}}
=== Interrupt Vector Request ($B0 read) ===
<pre>
7  bit  0
---- ----
vvvv vvvv
|||| ||||
|||| ||||
++++-++++- Interrupt vector offset
++++-++++- Interrupt vector requested
           (lowest three bits ignored)
           from the CPU.
</pre>
</pre>


=== Interrupt Enable ===
* Bits <code>7 .. 3</code> of this will always equal the user-provided vector offset.
* Bits <code>2 .. 0</code> of this will always equal the highest set bit index of Interrupt Status; if all bits in Interrupt Status are clear, they will equal <code>0</code>.
 
{{Anchor|Interrupt Enable}}
 
=== Interrupt Enable ($B2) ===


<pre>
<pre>
Line 90: Line 111:
</pre>
</pre>


=== Interrupt Status ===
Contrary to other systems, this also controls whether interrupts set the relevant bit in Interrupt Status.
 
{{Anchor|Interrupt Status}}
 
=== Interrupt Status ($B4 read)===


<pre>
<pre>
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</pre>
</pre>


=== Interrupt Acknowledge ===
{{Anchor|Interrupt Acknowledge}}
=== Interrupt Acknowledge ($B6 write)===


<pre>
<pre>
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</pre>
</pre>


=== Interrupt NMI Control ===
{{Anchor|Interrupt NMI Control}}
=== Interrupt NMI Control ($B7)===


<pre>
<pre>
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---- ----
---- ----
...b ....
...b ....
  |
   +----- Enable NMI on low battery detection
   +----- Enable NMI on low battery detection
</pre>
</pre>

Latest revision as of 12:00, 8 March 2025

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 enabled and the prerequisite condition is true,
    • Edge - will only be requested while enabled the moment the prerequisite condition becomes true.

Interrupt requests happen when the condition is true and the interrupt is enabled. Note that edge interrupts are only requested once; level interrupts are requested constantly, making acknowledgements ineffective until the condition is cleared or the interrupt is disabled. However, neither disabling an interrupt nor satisfying the condition clears the acknowledgement bit.

The user can additionally make use of all 256 available 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)

Contrary to other systems, this also controls whether interrupts set the relevant bit in Interrupt Status.

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
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