secs-gem/docs/16_e90_e157_substrates_modules.md

# 16 — E90 + E157: Substrate and module tracking

← [15 E87 — Carriers and load ports](15_e87_carriers.md) | [Back to index](00_index.md) | Next: [17 E116 + E120 + E39 — Performance, CEM, objects](17_e116_e120_e39_objects.md) →

E87 (chapter 15) tracks the **container**.  E90 and E157 track
what's *inside* the container — every individual wafer (substrate)
and every process module the wafer passes through.

This chapter is shorter than the others in Part 2 because the
ideas overlap E87 (the same three-orthogonal-axes pattern repeats)
and E40 (state events drive S6F11 CEIDs).

---

## E90 — Substrate tracking

### What it tracks

One state-bearing record **per wafer**, identified by a substrate
ID (an ASCII string, often the laser-etched serial number).

E90 has **three orthogonal axes** — the same pattern as E87's
carrier (chapter 15 §3):

#### 1. Substrate State (STS) — location

```cpp
// include/secsgem/gem/substrate_state.hpp:26
enum class SubstrateState : uint8_t {
  AtSource         = 0,    // in its origin carrier slot
  AtWork           = 1,    // in-process at a module
  AtDestination    = 2,    // delivered to final location
  NoState          = 255,
};
```

Events: `Acquire` (Source→Work), `Release` (Work→Destination),
`Return` (Work→Source, for unprocessed return).

#### 2. Substrate Processing State (SPS) — lifecycle

```cpp
enum class SubstrateProcessingState : uint8_t {
  NeedsProcessing = 0,
  InProcess       = 1,
  Processed       = 2,
  Aborted         = 3,
  Stopped         = 4,
  Rejected        = 5,
  Lost            = 6,
  Skipped         = 7,
  NoState         = 255,
};
```

Events: `StartProcessing`, `EndProcessing`, `Abort`, `Stop`,
`Reject`, `ReportLost`, `Skip`.

#### 3. Substrate ID Status — identity confidence

```cpp
enum class SubstrateIDStatus : uint8_t {
  NotConfirmed   = 0,
  WaitingForHost = 1,
  Confirmed      = 2,
  Mismatched     = 3,
  NoState        = 255,
};
```

Mirrors the `CarrierIDStatus` pattern from E87 — same problem
(equipment reads ID, host may need to verify), same shape of
solution.

### Why three axes?

The same reason E87 has three: these aspects evolve **at different
times** and **for different reasons**.

- A wafer can be `AtWork` + `NeedsProcessing` (just arrived,
  recipe hasn't started).
- A wafer can be `AtWork` + `InProcess` (recipe running).
- A wafer can be `AtSource` + `Processed` + `Confirmed` (back in
  its carrier slot after processing — typical end state).

Putting all three in one enum would multiply to ~30 valid
combinations.  Three independent FSMs with ~3 events each is much
cleaner.

### Code

State machines:
[`include/secsgem/gem/substrate_state.hpp`](../include/secsgem/gem/substrate_state.hpp)
defines `SubstrateStateMachine`, which composes the three.

Store:
[`include/secsgem/gem/store/substrates.hpp`](../include/secsgem/gem/store/substrates.hpp)
holds one record per substrate ID, with a Location string the
application updates as the wafer moves.

Tests:
[`tests/test_substrates.cpp`](../tests/test_substrates.cpp) (14
cases — every axis, every event); persistence in
[`tests/test_substrate_persistence.cpp`](../tests/test_substrate_persistence.cpp)
(7 cases).

CEID-on-wire emission ("Substrate StartProcessing fires the
configured SubstrateInProcess CEID") is verified by
[`tests/test_wire_ceid_emission.cpp`](../tests/test_wire_ceid_emission.cpp).

### Wire interaction

E90 doesn't define its own S/F messages — substrate state changes
fire as **CEIDs** that the host has subscribed to via the standard
E30 §6.6 Dynamic Event Report Configuration (chapter 13).  So:

- Equipment fires `Acquire` event on substrate `W-2026-06-09-A47`.
- `SubstrateStateMachine` transitions Source → Work.
- The state-change handler looks up the configured CEID for
  "SubstrateInProcess" (from `data/equipment.yaml`).
- That CEID fires → `compose_reports_for(ceid)` → `S6F11`.

Host gets one S6F11 per wafer transition.  In a 25-wafer FOUP
that's 25–50 events per processing pass.  Persistent reports +
spool (chapter 13 Additionals) handle the burst.

---

## E157 — Module Process Tracking

### What it tracks

One state-bearing record **per process module**.  A cluster tool
has multiple modules (Chamber A, Chamber B, Pre-clean, …); each
runs its own recipe step in parallel or sequence.  E157 lets the
host see *which module is in which step of which recipe right
now*.

### The states

```cpp
// include/secsgem/gem/module_state.hpp:20
enum class ModuleState : uint8_t {
  NotExecuting     = 0,
  GeneralExecuting = 1,   // setup, pre-process, post-process
  StepExecuting    = 2,   // actively running a recipe step
  StepCompleted    = 3,
  NoState          = 255,
};
```

Events: `StartGeneral`, `StartStep`, `CompleteStep`, `Reset`,
`Abort`.

Notice this is a much simpler FSM than E90 — one axis only.  That's
because modules are more deterministic than substrates: a module
is either running a step or it isn't; substrates can be in many
overlapping conditions.

### Code

[`include/secsgem/gem/module_state.hpp`](../include/secsgem/gem/module_state.hpp)
defines `ModuleStateMachine`.

Store:
[`include/secsgem/gem/store/modules.hpp`](../include/secsgem/gem/store/modules.hpp).

Tests:
[`tests/test_modules.cpp`](../tests/test_modules.cpp) (5 cases).

### How E157 plays with E40 and E90

Concrete example.  A PVD tool with three modules (Chamber A, B,
C); host submits PJ for wafer W-1, recipe says "process at
Chamber B for 90 seconds":

```
1. PJ-1 transitions Queued → SettingUp → WaitingForStart → Processing.
   (E40 FSM, chapter 14)
2. Equipment fires ModuleEvent::StartGeneral on Chamber B.
   ModuleState: NotExecuting → GeneralExecuting.
   (E157 FSM)
3. Equipment fires SubstrateEvent::Acquire on W-1.
   Substrate STS: AtSource → AtWork.
   (E90 FSM)
4. Recipe step begins.  ModuleEvent::StartStep on Chamber B.
   ModuleState: GeneralExecuting → StepExecuting.
   Substrate SPS: NeedsProcessing → InProcess.
5. ...90 seconds pass...
6. Recipe step ends.  ModuleEvent::CompleteStep on Chamber B.
   ModuleState: StepExecuting → StepCompleted.
   Substrate SPS: InProcess → Processed.
7. Substrate released.  SubstrateEvent::Release on W-1.
   Substrate STS: AtWork → AtDestination.
8. PJ-1: ProcessComplete.
```

Each of the eight transitions fires a CEID, which fires an S6F11
event report.  The host sees the **complete trace** of where every
wafer was at every moment.

---

## Where to go next

You now know how every component of in-flight material is
tracked.  The next chapter covers the three smaller GEM 300
standards that round out the suite: equipment performance time
tracking, the common equipment model, and generic object
services.

Next: [→ 17 E116 + E120 + E39 — Performance, CEM, objects](17_e116_e120_e39_objects.md)