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

   1 = IRQ enabled (IMR)

   +----------+-------------------------------------------------------+
   | Bit 7    |   1 = if you want to set another bit(s)               |
   |          |   0 = if you want to clear another bit(s)             |
   | 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.

   If you set or clear specific bits in $D01A, the others remain
   untouched.