FANCO-16 v7 — ADDITIVE SIREN AND PHYSICAL KEYBOARD
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CPU encoding, graphics, timer and atomic stores match v6. The virtual cycle
clock is 60,000,000 Hz (v6: 120,000,000 Hz); the timer period is 60000000/Hz.
Applications identify themselves with ASCII FAN1 then byte 07. V6 and
unversioned programs are rejected before resetting or changing memory.

Memory (hexadecimal)
0000–000F  CPU registers
0010–0015  IRQ vector, 16-bit timer Hz, active flag, missed-tick count
0020–0027  Existing buttons and pointer
0040–005F  SID-friendly aliases to the SAME first three SIREN operators
0060–006D  Blitter
0070–0078  RGBA graphics
0080–00A7  Ten touch slots
00D0–00E7  Two audio capture descriptors
0100–02FF  Sixteen 32-byte SIREN operators
0300–0327  Eight five-byte mixer slots
0328–0342  Three nine-byte filters
0343       Coarse master
0344–03F3  Eight 22-byte two-tap delay lines
03F4–03F5  Chip control rate, initially 600 Hz
03F6       Status; write one to acknowledge an error
03F7       Fine master
03F8–03FF  Reserved
0400–041F  Keyboard DOWN bitmap (read-only)
0420–043F  Keyboard PRESSED bitmap (write-one-to-clear)
0440–045F  Keyboard RELEASED bitmap (write-one-to-clear)
0460–047F  Reserved keyboard control space (read-only zero)
0480–FFFF  Program/data/stack RAM

Keyboard key IDs follow USB HID Keyboard/Keypad usage IDs, 0–255.
byte = key >> 3; mask = 1 << (key & 7). Physical Z is ID 1D:
check bit 20 at 0403 for held, or 0423 for a new press. Write 20 to
0423 to acknowledge only that press. Release events appear at 0443.
Host repeat does not create a second press. A tap between polls can
set both edges. Focus loss releases held keys and sets release edges.
Bitmaps retain one occurrence of each edge, not an ordered event queue.

/v7/ runs piano.asm, a self-contained guest program: its 100 Hz IRQ polls
the keyboard bitmaps and touch slots, allocates eight additive voices with
six shared extension banks, advances measured two-stage per-partial decays,
handles dampers and the sustain pedal, and draws its own keyboard. The older
host-driven page remains at /v7/piano/.

Custom-envelope pointers must be zero or 0480–FFF7. Pointer writes snapshot
nine envelope bytes at retirement, preserving v6 atomic preflight behavior.