Read-only diagnostic to disambiguate the three causes folded into
LPDDR_STATUS[5]. bit5 (0x02C) semantics are UNCHANGED.
- gs_lpddr_scanout_lb: register a live (rd_errs!=0) flag in the emif
domain (the raw counter never crosses), and capture the FIRST raw
underflow of each video-source-enabled session as a bundled-data
snapshot (scan_y/nf_v/nf_s0 + base-vs-lookahead cause + line_valid +
vphase), held stable until !enable. The existing sticky underflow_v
latch, fetch FSM, pixel path and arbitration are untouched.
- ps2_hps_bridge: independently 2-FF sync the two split live flags;
latch the snapshot on the rising synced-valid edge (coherent bundled
data). New read-only regs 0x120 SCAN_DIAG_STATUS / 0x124
SCAN_DIAG_FIRST (window addr[37:5]==9); 0x118/0x11C reserved slots
untouched.
- top: drive 5 diag nets per scanout arm like scan_err_w; bit5 assign
unchanged.
- tb_gs_scanout_diag (new): provokes AXI RRESP error, cold-start row-0
starvation, first-failure capture + coherent bridge readback, and
clear-via-video-source-disable (17/17 checks).
- Tie off the new bridge inputs in the four .*-instantiating TBs.
Sim set all PASS: focused TB, tb_ps2_hps_bridge, scanout_lb
{binomial,hstretch,psm32_256}, and the complete f52 replay (FB
byte-identical: Z 0/307200, COLOR 0/245760; sum32=0xaad0b94d).
No fix / gray-code / persistence-filter / scanout checksum. No Quartus,
no board, no push.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
rtl/gif_gs
GIF path and Graphics Synthesizer logic. Matches docs/contracts/gif_gs.md.
Current contents
-
gs_stub.sv— GS shell with two architecturally distinct write ports (Ch75 namespace split):reg_wr_*— privileged-block writes (16-bit offset within0x12000000). LatchesBGCOLOR(offset0x00E0) intobg_{r,g,b}; other offsets emitEV_MODE.gif_reg_*— GIF A+D register-number writes (8-bit reg# + 64-bit data). DecodesPRIM=0x00,RGBAQ=0x01,XYZF2=0x04,XYZ2=0x05,FRAME_1=0x4C,ZBUF_1=0x4Einto per-register 64-bit latches; unknown reg numbers emitEV_MODE.- No VRAM, no drawing yet — that is the next architectural step.
-
gif_path_stub.sv— Wave 2 minimal GIF packet logger; project-local single-qword register-write format. Used bytb_bgcolor_via_dma. -
gif_packed_stub.sv— real PS2 GIFtag parser (Ch72-Ch75). Handles PACKED (FLG=0), REGLIST (FLG=1), IMAGE (FLG=2), DISABLE (FLG=3). TheREAL_AD_REG_MAPparameter selects the A+D dispatch port:REAL_AD_REG_MAP=0(default, back-compat) — drivesgs_stub.reg_wr_*using a project-local 16-bit offset carried inin_data[79:64].REAL_AD_REG_MAP=1— drivesgs_stub.gif_reg_*using the real PS2 8-bit reg# carried inin_data[71:64]. Source-of-truth: PCSX2GSRegs.h.
BGCOLOR reset value
At reset, bg_{r,g,b} default to 0x40 each (mid-grey) rather than black.
Rationale: this makes "gs_stub reset but no BGCOLOR write yet" visually
distinct from "video output disabled / black frame" in Milestone A. Override
is a BGCOLOR write from the test harness.
Pitfall: namespace conflation
Ch74 conflated GIF A+D reg numbers with GS privileged-block offsets and
mapped e.g. 0x14→PMODE@0x0000. That is fiction — those are separate
namespaces. Ch75 split them. ZBUF_1 is 0x4E, not 0x4F (that's
ZBUF_2). When adding a new GIF-context register, source the reg# from
PCSX2 GSRegs.h, never from the privileged-block map.