FPGA-Neural

16 Commits 5 Branches 1 Tag

3 Commits

Include renames

Author	SHA1	Message	Date
micheleandClaude Sonnet 5	7e2711fa27	feat: widen ADDR_WIDTH to 23 bits for full 8MB PSRAM addressing Bumps ADDR_WIDTH's default from 22 to 23 bits across every RTL module (neuron_memory, layer_sequencer, spi_engine, spi_neuron_top, mem_arbiter, int8_memory_access, memory_interface, psram_controller, memory_model) and every testbench that mirrors it, so the system's byte-address space reaches the full 8 MiB the recommended PSRAM part (ISSI IS66WVE4M16EBLL-70BLI, docs/FPGA-Neural-Hardware-Design.md §3) actually provides -- previously only 4 MiB (half the chip) was reachable, since int8_memory_access.v's byte->word address shift (addr >> 1) turned the old 22-bit byte address into only 21 real word bits, one short of the chip's real 22-bit word address (A0-A21). At 23 bits, that same shift lands exactly on all 22 chip address lines, so the whole part is usable now instead of deferred to a future widening. Also fixes a stray 22'd11-sized literal in layer_sequencer.v's descriptor-table address increment (numerically already safe via Verilog's zero-extension, but now correctly unsized so it always matches ADDR_WIDTH instead of silently assuming 22). Updated docs/FPGA-NeuralNetwork-Engine.md's SPI protocol address-field note (23 bits, top 1 reserved bit instead of 2) and docs/FPGA-Neural-Hardware-Design.md's PSRAM section (the "chip has one spare address line" framing is gone now that all 22 are wired and used). Full regression (all 11 ADDR_WIDTH-touching testbenches, plus a Yosys elaboration check of spi_neuron_top with the new default and no override) passes clean. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01WQV3vS9TXaGDJ5cRfnfidt	2026-09-02 21:00:46 +02:00
michele	233d6ff7fb	feat: complete Phase 5 multi-layer network (RUN_NETWORK) + fix STATUS race Wires the already-present layer_sequencer.v into the SPI stack: - spi_engine.v: RUN_NETWORK opcode (0x23) + SET_BASE selectors for table_base/buf_a_base/buf_b_base; STATUS.busy/done extended to track the sequencer (seq_busy/seq_done) alongside neuron_memory directly, so done latches on the last layer only. - spi_neuron_top.v: instantiates layer_sequencer, muxes neuron_memory's control inputs between it (while seq_busy) and spi_engine's direct-drive path (legacy single-layer mode), wires the sequencer's own RAM master to mem_arbiter's Port C. Found and fixed a real race while writing the end-to-end test: STATUS's sticky/clear-on-read done bit read its value live/combinationally during transmission and cleared unconditionally on any STATUS read. A done_event landing mid-transmission of a STATUS response byte could be silently dropped -- the host would receive a stale byte while the sticky bit was cleared regardless, hanging any host polling STATUS in a loop. Present since Phase 4, not RUN_NETWORK-specific; only surfaced under this test's continuous polling. Fixed by latching a status_snapshot at opcode-accept time and gating the clear on what was actually transmitted. Tests: spi_engine_tb.v gains RUN_NETWORK/SET_BASE opcode tests (K/L); new layer_sequencer_tb.v unit-tests the sequencer FSM directly (descriptor table, ping-pong buffer addressing, byte-exact copy-out); new spi_neuron_top_runnetwork_tb.v drives a real 2-layer network over simulated SPI end to end (real neuron_memory + PSRAM, hand-computed expected output) and confirms the legacy single-layer path still works afterward. All existing testbenches still pass.	2026-09-02 19:47:36 +02:00
micheleandClaude Sonnet 5	a2bd60e305	feat: complete Phase 4 SPI RTL (engine, arbiter, top) + real-RAM e2e test Implements the rest of the SPI interface (docs §8.1) on top of spi_slave.v from the previous commit: - rtl/spi_engine.v: opcode FSM + register bank, all 8 opcodes (NOP, WRITE_RAM, READ_RAM, RESET, SET_BASE, START, STATUS, READ_OUTPUT, READ_CONFIG). tx_byte is driven combinationally from live state (not reactively on tx_byte_req), applying the prefetch-vs-consume contract documented on spi_slave.v. STATUS.done is a sticky, clear-on-read latch. RAM master port uses the same byte-level convention as neuron_memory.v's external mem_* port. - rtl/mem_arbiter.v: fixed-priority (neuron_memory > spi_engine) grant-and-forward arbiter sharing one byte-level memory port between spi_engine's WRITE_RAM/READ_RAM and neuron_memory's own X/W/bias reads during a run. - rtl/spi_neuron_top.v: full integration -- spi_slave -> spi_engine -> mem_arbiter -> a single shared int8_memory_access -> memory_interface -> psram_controller -> PSRAM pins. neuron_memory's rst is global rst OR'd with the RESET opcode's soft-reset pulse. The host has no direct electrical path to the RAM, only through this chain. Testing: - sim/spi_engine_tb.v: 10 tests (one per opcode + WRITE_RAM/READ_RAM, START idle-vs-busy, STATUS sticky/clear-on-read, extra-MOSI-bytes- ignored, back-to-back transactions) against a synthetic 2-cycle- latency RAM model, isolating the opcode FSM from PSRAM timing. Found and fixed two testbench-only bugs (RTL needed no change): the same delta-zero clock-edge race as spi_slave_tb.v (blocking `nm_done=1` landing on the same sim time as a posedge -- fixed via negedge-based pulsing) and a missing RAM sentinel initialization. - sim/spi_neuron_top_tb.v: end-to-end test against the real psram_model.v (not a mock) -- RESET/READ_CONFIG/WRITE_RAM/ READ_RAM/SET_BASE/START/STATUS/READ_OUTPUT all driven purely over simulated SPI. 3/3 scenarios (sum, saturation, ReLU) pass on the first attempt; confirms the arbiter and shared byte<->word bridge are correct against real PSRAM timing, not just a synthetic mock. Real-toolchain verification (Yosys + nextpnr-ecp5 + ecppack): spi_slave.v and spi_engine.v synthesize clean and comfortably clear 80 MHz in isolation (403 MHz / 191 MHz, no DSP usage). The full spi_neuron_top.v integration, however, does NOT meet 80 MHz (~52-56 MHz depending on PARALLEL) -- the critical path is entirely inside neuron_parallel.v's existing saturation comparator (no contribution from the new SPI/arbiter logic), but its routed delay is ~57% worse than in the isolated benchmark due to placement/ routing congestion once SPI + PSRAM logic shares the fabric with it, not resource exhaustion (2% DSP usage). Documented as a Phase 4/7 finding in docs/FPGA-NeuralNetwork-Engine.md -- a floorplanning/ pipelining problem for Phase 7, not a functional-correctness issue (verified independently in simulation against real PSRAM timing). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01WQV3vS9TXaGDJ5cRfnfidt	2026-09-02 15:44:03 +02:00

Author

SHA1

Message

Date

micheleandClaude Sonnet 5

7e2711fa27

feat: widen ADDR_WIDTH to 23 bits for full 8MB PSRAM addressing

Bumps ADDR_WIDTH's default from 22 to 23 bits across every RTL
module (neuron_memory, layer_sequencer, spi_engine, spi_neuron_top,
mem_arbiter, int8_memory_access, memory_interface, psram_controller,
memory_model) and every testbench that mirrors it, so the system's
byte-address space reaches the full 8 MiB the recommended PSRAM part
(ISSI IS66WVE4M16EBLL-70BLI, docs/FPGA-Neural-Hardware-Design.md §3)
actually provides -- previously only 4 MiB (half the chip) was
reachable, since int8_memory_access.v's byte->word address shift
(addr >> 1) turned the old 22-bit byte address into only 21 real word
bits, one short of the chip's real 22-bit word address (A0-A21). At
23 bits, that same shift lands exactly on all 22 chip address lines,
so the whole part is usable now instead of deferred to a future
widening.

Also fixes a stray 22'd11-sized literal in layer_sequencer.v's
descriptor-table address increment (numerically already safe via
Verilog's zero-extension, but now correctly unsized so it always
matches ADDR_WIDTH instead of silently assuming 22).

Updated docs/FPGA-NeuralNetwork-Engine.md's SPI protocol address-field
note (23 bits, top 1 reserved bit instead of 2) and
docs/FPGA-Neural-Hardware-Design.md's PSRAM section (the "chip has
one spare address line" framing is gone now that all 22 are wired
and used).

Full regression (all 11 ADDR_WIDTH-touching testbenches, plus a
Yosys elaboration check of spi_neuron_top with the new default and
no override) passes clean.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WQV3vS9TXaGDJ5cRfnfidt

2026-09-02 21:00:46 +02:00

michele

233d6ff7fb

feat: complete Phase 5 multi-layer network (RUN_NETWORK) + fix STATUS race

Wires the already-present layer_sequencer.v into the SPI stack:

- spi_engine.v: RUN_NETWORK opcode (0x23) + SET_BASE selectors for
  table_base/buf_a_base/buf_b_base; STATUS.busy/done extended to
  track the sequencer (seq_busy/seq_done) alongside neuron_memory
  directly, so done latches on the last layer only.
- spi_neuron_top.v: instantiates layer_sequencer, muxes
  neuron_memory's control inputs between it (while seq_busy) and
  spi_engine's direct-drive path (legacy single-layer mode), wires
  the sequencer's own RAM master to mem_arbiter's Port C.

Found and fixed a real race while writing the end-to-end test: STATUS's
sticky/clear-on-read done bit read its value live/combinationally
during transmission and cleared unconditionally on any STATUS read.
A done_event landing mid-transmission of a STATUS response byte could
be silently dropped -- the host would receive a stale byte while the
sticky bit was cleared regardless, hanging any host polling STATUS in
a loop. Present since Phase 4, not RUN_NETWORK-specific; only
surfaced under this test's continuous polling. Fixed by latching a
status_snapshot at opcode-accept time and gating the clear on what
was actually transmitted.

Tests: spi_engine_tb.v gains RUN_NETWORK/SET_BASE opcode tests (K/L);
new layer_sequencer_tb.v unit-tests the sequencer FSM directly
(descriptor table, ping-pong buffer addressing, byte-exact copy-out);
new spi_neuron_top_runnetwork_tb.v drives a real 2-layer network over
simulated SPI end to end (real neuron_memory + PSRAM, hand-computed
expected output) and confirms the legacy single-layer path still
works afterward. All existing testbenches still pass.

2026-09-02 19:47:36 +02:00

micheleandClaude Sonnet 5

a2bd60e305

feat: complete Phase 4 SPI RTL (engine, arbiter, top) + real-RAM e2e test

Implements the rest of the SPI interface (docs §8.1) on top of
spi_slave.v from the previous commit:

- rtl/spi_engine.v: opcode FSM + register bank, all 8 opcodes (NOP,
  WRITE_RAM, READ_RAM, RESET, SET_BASE, START, STATUS, READ_OUTPUT,
  READ_CONFIG). tx_byte is driven combinationally from live state
  (not reactively on tx_byte_req), applying the prefetch-vs-consume
  contract documented on spi_slave.v. STATUS.done is a sticky,
  clear-on-read latch. RAM master port uses the same byte-level
  convention as neuron_memory.v's external mem_* port.
- rtl/mem_arbiter.v: fixed-priority (neuron_memory > spi_engine)
  grant-and-forward arbiter sharing one byte-level memory port
  between spi_engine's WRITE_RAM/READ_RAM and neuron_memory's own
  X/W/bias reads during a run.
- rtl/spi_neuron_top.v: full integration -- spi_slave -> spi_engine
  -> mem_arbiter -> a single shared int8_memory_access ->
  memory_interface -> psram_controller -> PSRAM pins. neuron_memory's
  rst is global rst OR'd with the RESET opcode's soft-reset pulse.
  The host has no direct electrical path to the RAM, only through
  this chain.

Testing:
- sim/spi_engine_tb.v: 10 tests (one per opcode + WRITE_RAM/READ_RAM,
  START idle-vs-busy, STATUS sticky/clear-on-read, extra-MOSI-bytes-
  ignored, back-to-back transactions) against a synthetic 2-cycle-
  latency RAM model, isolating the opcode FSM from PSRAM timing.
  Found and fixed two testbench-only bugs (RTL needed no change):
  the same delta-zero clock-edge race as spi_slave_tb.v (blocking
  `nm_done=1` landing on the same sim time as a posedge -- fixed via
  negedge-based pulsing) and a missing RAM sentinel initialization.
- sim/spi_neuron_top_tb.v: end-to-end test against the **real**
  psram_model.v (not a mock) -- RESET/READ_CONFIG/WRITE_RAM/
  READ_RAM/SET_BASE/START/STATUS/READ_OUTPUT all driven purely over
  simulated SPI. 3/3 scenarios (sum, saturation, ReLU) pass on the
  first attempt; confirms the arbiter and shared byte<->word bridge
  are correct against real PSRAM timing, not just a synthetic mock.

Real-toolchain verification (Yosys + nextpnr-ecp5 + ecppack):
spi_slave.v and spi_engine.v synthesize clean and comfortably clear
80 MHz in isolation (403 MHz / 191 MHz, no DSP usage). The full
spi_neuron_top.v integration, however, does NOT meet 80 MHz
(~52-56 MHz depending on PARALLEL) -- the critical path is entirely
inside neuron_parallel.v's existing saturation comparator (no
contribution from the new SPI/arbiter logic), but its routed delay
is ~57% worse than in the isolated benchmark due to placement/
routing congestion once SPI + PSRAM logic shares the fabric with
it, not resource exhaustion (2% DSP usage). Documented as a Phase
4/7 finding in docs/FPGA-NeuralNetwork-Engine.md -- a floorplanning/
pipelining problem for Phase 7, not a functional-correctness issue
(verified independently in simulation against real PSRAM timing).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WQV3vS9TXaGDJ5cRfnfidt

2026-09-02 15:44:03 +02:00