ADR 0010: PTO v0 ACR routing and context reset

Context

PTO exposes ACR0 through ACR15, banked context-family system registers, and a shared trap envelope. The earlier reference profile routed an ACR1 fault to ACR0, routed only ACR2 to ACR1, left ACR3 through ACR15 implicit, and reset only the ACR0 extended-register bank. It also assigned the system-call trap number to bundle-control faults even though the catalog defines separate bundle-trap and system-call identities.

Decision

• ACR0 is the root manager, ACR1 is the system manager, and ACR2 through ACR15 are managed rings in the PTO v0 profile.
• A synchronous fault or interrupt sourced in ACR0 targets ACR0.
• A synchronous fault or interrupt sourced in ACR1 targets ACR1.
• A synchronous fault or interrupt sourced in ACR2 through ACR15 targets ACR1.
• Reset clears the complete catalog-defined context-family low-index range in all 16 ACR banks.
• Reset also clears every live GPR, T/U queue, P1 through P7, the bundle descriptor, tile descriptor and definedness bit, reservation, memory/event, fault, trap, and saved-context field. P0 is hardwired all-ones. Profile constants are then installed explicitly.
• Bundle-format and bundle-control faults report BUNDLE_TRAP (5).
• SCALL (6) remains reserved for the separately specified ACRC service- request transition and is not used as a bundle-control surrogate.

ADRs 0011, 0012, 0018, and 0019 define the visible trap snapshot, ACRC request routing, ACRE restoration, trap disposition, and predicate preservation that complete this reset envelope.

Consequences

The routing function is total over all 16 ACRs. Reset cannot leak architectural state between executions through a nonzero ACR bank, high register index, predicate, tile, bundle descriptor, reservation, or saved context. Nonzero-seed tests cover the lowest and highest boundaries and every trap bank.