     $D01A/53274/VIC+26:  VIC Interrupt Mask Register (IMR)

       1 = IRQ enabled

       +----------+-------------------------------------------------------+
       | Bit 7-4  |   Always 1                                            |
       | Bit 3    |   Light-Pen Triggered IRQ Flag                        |
       | Bit 2    |   Sprite to Sprite Collision IRQ Flag     (see $D01E) |
       | Bit 1    |   Sprite to Background Collision IRQ Flag (see $D01F) |
       | Bit 0    |   Raster Compare IRQ Flag                 (see $D012) |
       +----------+-------------------------------------------------------+

       An IRQ will be initiated, if equal bits are set in IRR and IMR.
       Default Value: $00/0 (%00000000).