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BUS16

Honest summing of all tile contributions

๐Ÿ“Š Bus Physics

Configuration

Parameter Value
Lanes 8 lane (BUS16[0..7])
Level Level16 (0..15)
Mode Summing in PHASE_WRITE
Policy Saturate (clamp15), no wrap

๐Ÿงฎ Contribution Summing

In PHASE_WRITE for each lane i=0..7:

contrib_from_all_tiles[i] = ฮฃ drive_vec[t][i]
  for all t where:
    - (routing_flags16[t] & BUS_W) != 0
    - locked self OR locked_ancestor

bus_raw[i] = contrib_from_all_tiles[i]
BUS16[i] = clamp15(bus_raw[i])
BUS_CLIP[i] = (bus_raw[i] > 15)

Ranges

Value Range
bus_raw [0..3840] (256 tiles ร— 15)
BUS16 [0..15] (clamped)

๐Ÿšจ CLIP / OVF Flags

BUS_CLIP

BUS_CLIP[i] = (bus_raw[i] > 15)
BUS_CLIP_ANY = OR_i BUS_CLIP[i]

BUS_OVF

BUS_OVF_ANY = BUS_CLIP_ANY
OVF_ANY = BUS_OVF_ANY

Policy v0.2: only saturate (clamp15), no wrap/divide.

๐Ÿ”„ Phase Discipline

READ Phase

  • Conductor drives VSB[0..7]
  • Island does NOT drive BUS
  • Tiles read VSB_INGRESS

TURNAROUND

Conductor: Hi-Z / no-drive VSB
Island: prepare drive BUS

WRITE Phase

  • Conductor: Hi-Z VSB
  • Island drives BUS16
  • Tiles with BUS_W=1 and locked write drive_vec

READOUT_SAMPLE

R0_RAW_BUS: readout = BUS16[0..7] as 8ร—Level16

๐ŸŽฏ BUS Write Conditions

A tile writes to BUS16 only if:

  1. BUS_W == 1 (routing_flags16 & 0x0200)
  2. locked self OR locked_ancestor (has locked ancestor in activation graph)

Drive Vector

if locked_after == 1:
  drive_vec[i] = in16[i]  # passthrough
else:
  drive_vec[i] = row16_out[i]  # computed from weights

๐Ÿ“ Calculation Example

Given

  • 3 tiles write to lane 0
  • drive_vec[0] = [10, 5, 8]

Calculation

bus_raw[0] = 10 + 5 + 8 = 23
BUS16[0] = clamp15(23) = 15
BUS_CLIP[0] = true (23 > 15)

๐Ÿ”— Relation to VSB

Plane Direction Phase
VSB[0..7] Conductor โ†’ Island READ
BUS16[0..7] Island โ†’ Conductor WRITE

Important: Data is not sent to neighbors. Neighbors only form activation graph for BUS read permission.

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