d79f59d24e
mission-phase-timers.md left 180 open as "a limit and a warning
threshold is the obvious reading, but not established". Reading
sub_822639B8 -- ScriptPhase::Update 0x82263528, same dt as the
stopwatch bank -- settles it the other way:
if running: [+304] += dt
if armed: [+308] -= dt while [+308] > 0
else [+312] -= dt, clamped at 0
[+312] is never compared with [+308]; it is decremented, and only in
the A<=0 arm. Two sequential countdowns. Disc-wide the second
argument is 180 in all 29 timer_set sites while the first varies
(600 x19, 1200 x8, 900, 1800).
Built-ins 123-127 are vtable slots 90-94 on five scalars at
[phase+304..320]. 125 and 126 have ZERO call sites in all 28 scripts:
the script arms, starts and stops this clock but never reads it.
Corrects mission-phase-timers.md, which merged this clock with
stopwatch 0 -- timer_resume starts [+304], set_flag(0) one instruction
later starts the stopwatch the timeline's kind=0 reads.
Docs only; all seven ISL artefacts regenerate byte-identical.
123 lines
5.0 KiB
Markdown
123 lines
5.0 KiB
Markdown
# ✅ The MISSION timer is a second, separate clock — and `timer_set`'s second argument is a second COUNTDOWN
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`mission-phase-timers.md` left this open: "`timer_set`'s second argument (`180`)
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— a limit and a warning threshold is the obvious reading, but it is **not**
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established." It is established now, and **the obvious reading is wrong**.
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This clock has nothing to do with the 32 stopwatches in
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[isl-timers](isl-timers.md); it is five separate scalar fields on the same
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ScriptPhase, driven by its own updater.
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## The five fields
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Zeroed together by `sub_8225FEF8` (`0x82260084`–`0x82260098`):
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| field | type | meaning |
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|---|---|---|
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| `[phase+304]` | f32 | **elapsed**, counts **up** |
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| `[phase+308]` | f32 | **countdown A**, counts **down** |
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| `[phase+312]` | f32 | **countdown B**, counts down *only after A reaches 0* |
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| `[phase+316]` | int | **running** — gates the elapsed counter |
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| `[phase+320]` | int | **armed** — gates the two countdowns |
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## The five built-ins
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All are stubs into the ScriptPhase vtable, slots 90–94
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(`0x8226C690`–`0x8226C6F0`):
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| built-in | slot | what it does | calls disc-wide |
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|---|---|---|---|
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| 127 `timer_set(a, b)` | 94 | `armed = 1; A = (f32)local[0]; B = (f32)local[1]` | 29 |
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| 123 `timer_resume` | 90 | `running = 1` | 40 |
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| 124 `timer_stop` | 91 | `running = 0; armed = 0` | 170 |
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| 125 `timer_reset` | 92 | `elapsed = A = B = 0.0; armed = 0` | **0** |
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| 126 `timer_elapsed` | 93 | returns `elapsed` as a double in `[phase+176]` | **0** |
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`timer_set` reads its two arguments as **doubles** at `0(r4)` and `8(r4)`, `r4`
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being the converted locals array — so `local[0]` and `local[1]`.
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## ✅ The update — `sub_822639B8(phase, dt)`
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Called from **`ScriptPhase::Update` at `0x82263528`**, with **`fmr f1, f30`** —
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the *same* `dt` the stopwatch bank gets at `0x82263480`. So this clock counts
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the same **seconds** ([isl-timers](isl-timers.md)), and `600 / 900 / 1200 / 1800`
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and `180` are 10 / 15 / 20 / 30 minutes and 3 minutes.
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```
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822639C8 if [+316] != 0: [+304] += dt ; elapsed counts UP
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822639E4 if [+320] != 0:
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822639F4 if [+308] > 0.0: [+308] -= dt ; A counts down ...
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82263A00 else: [+312] -= dt ; ... then B does
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82263A10 if [+312] < 0.0: [+312] = 0.0
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```
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### 🔴 That refutes "a limit and a warning threshold"
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A threshold would be **compared** against the countdown. `[+312]` is never
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compared with `[+308]` anywhere. It is *decremented*, and the `bc 12, gt`
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at `0x822639FC` jumps **away** to the `A -= dt` arm — so `B -= dt` runs **only**
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in the `A <= 0` branch. The two are **sequential countdowns**: a per-mission
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period, then a fixed second period.
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## ✅ Every mission agrees, and the second value never varies
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29 `timer_set` sites across the disc:
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| first argument | sites |
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|---|---|
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| 600 | 19 |
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| 1200 | 8 |
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| 900 | 1 (Stage 26) |
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| 1800 | 1 (Stage 24) |
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| **second argument** | **180 in all 29** |
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A per-mission limit that varies, followed by a fixed 3-minute stage. Note this
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constancy is *consistent* with the sequential reading and does not by itself
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establish it — the disassembly above is what does.
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## ✅ What it feeds — and what it does not
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Each frame the updater allocates a 32-byte message (type tag `0xAB03E5BA`,
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vtable `0x820A8D68`) and posts it to the bus at `[0x828F35DC]`, carrying:
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```
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+24 = [phase+304] elapsed
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+28 = [phase+312] countdown B
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+16 = running ([+316] != 0)
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+20 = expired ([+320] == 1 && [+308] <= 0.0)
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```
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`expired` is exactly "countdown A has run out" — the point at which B starts.
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🔑 **The script never reads this clock.** `timer_elapsed` and `timer_reset` have
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**zero call sites in all 28 scripts**; the script only *arms* (127), *starts*
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(123) and *stops* (124) it. Its only consumer read here is the posted message.
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## 🔴 A conflation in `mission-phase-timers.md`, corrected
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That page says timer 0 "is started by `timer_set(1200, 180)` then
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`timer_resume`, with a 1200-second limit". Those are **two different clocks
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armed back to back**:
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```
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timer_set(1200, 180) -> this object: A = 1200, B = 180, armed
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timer_resume -> this object: elapsed starts counting
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set_flag(0) -> STOPWATCH 0 starts (isl-timers.md)
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```
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The timeline's `kind = 0` reads stopwatch 0, not `[phase+304]`. The two start in
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the same coroutine one instruction apart, which is why they read almost the same
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value and the conflation was invisible. **The 1200-second limit belongs to the
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mission timer; it is not stopwatch 0's limit.**
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## 🟡 Not settled
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* **Who subscribes to `0xAB03E5BA`.** The literal appears at exactly one site —
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the producer — but `0xAB03` is the high half of *many* message tags in this
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image and dispatch is not by literal compare, so a single occurrence is **not**
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evidence that nothing consumes it. Whether running out of time ends the mission
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is therefore unread.
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* What B counting to zero does. Nothing observed acts on it.
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* Whether `timer_stop`'s 170 sites are all phase teardown, or some are a real
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mid-mission stop.
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