Commodore Amiga A2000 - Interrupts; Table 7-5 Contents of the Beam Position Counter

Table 7-5: Contents of the Beam Position Counter
VPOSR Read-only Read the high bit of the vertical
position (V8) and the frame-type bit.
Bit 15 LOF (Long-framebit). Used to
initialize interlaced displays.
Bits 14-1 Unused
Bit 0 High bit of the vertical position
(V8). Allows PAL line counts (313) to
appear in PAL versions of the Amiga.
VHPOSR Read-only Read vertical and horizontal
position of the counter that is
producing the beam on the screen
(also reads the light pen).
Bits 15-8 Low bits of the vertical
position, bits V7-V0
Bits 7-0 The horizontal position, bits H8-H1.
Horizontal resolution is 1/160th
of the screen width.
VPOSW Write only Bits same as VPOSR above.
VHPOSW Write only Bits same as VHPOSR above.
Used for counter synchronization
with chip test patterns.
As usual, the address pairs VPOSR,VHPOSR and VPOSW,VHPOSW can be read from and
written to as long words, with the most significant addresses being VPOSR and VPOSW.
INTERRUPTS
This system supports the full range of 68000 processor interrupts. The various kinds of
interrupts generated by the hardware are brought into the peripherals chip and are
translated into six of the seven available interrupts of the 68000.
- System Control Hardware 211 -