SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

open-drain-command-engine

codex gpt-5.5 ✓ resolved GOOD_SUCCESS ↑ View task
Solved from the instruction alone, tests/ and solution/ were withheld from the agent's workspace and restored only for grading.
Reward = tests/test.sh exit code (0 → resolved); the classification below is post-hoc and cannot change it.
Classification , post-hoc; cannot change the reward
GOOD_SUCCESSLegitimate solve, implements the asked-for behavior; tests verify real functionality.
SubtypeLegitimate Solution
EvidenceTest output shows `mismatches=0 samples=2351` with all output signals matching expected behavior (cmd_ack=0, busy=0, al=0, bit_out=0, scl=0, sda=0 mismatches). Agent created TopModule with I2cBitCommandEngine instance. FSM implements all four commands (START, STOP, WRITE, READ) with proper phase sequencing: accept→setup→wait_high→done. Outputs are registered, reset is synchronous active-high, cmd_ack pulses for one cycle, al is sticky until reset. Open-drain control properly manages SCL/SDA release vs pull patterns. iverilog compilation succeeded with no warnings. Implementation correctly handles the complex timing constraint: `scl_i` high observation recorded only on clock edge, not affecting current phase outputs.
Root causeAgent successfully implemented a multi-state I2C bit controller from a complex timing specification. The solution correctly handles the key difficulty: delaying SCL-high observation effects until the next clock cycle through explicit registered phases (ST_*_WAIT_HIGH states). All 2,351 test vectors pass with zero mismatches.
RecommendationN/A - task is fine
Trajectory
Tool-by-tool agent trajectory
9 tool calls · 2 tool types · 19 steps
<permissions instructions> Filesystem sandboxing defines which files can be read or written. `sandbox_mode` is `danger-full-access`: No filesystem sandboxing - all commands are permitted. Network access is enabled. Approval policy is currently never. Do not provide the `sandbox_permissions` for any reason, commands will be rejected. </permissions instructions><apps_instructions> ## Apps (Connectors) Apps (Connectors) can be explicitly triggered in user messages in the format `[$app-name](app://{connector_id})`. Apps can also be implicitly triggered as long as the context suggests usage of available apps. An app is equivalent to a set of MCP tools within the `codex_apps` MCP. An installed app's MCP tools are either provided to you already, or can be lazy-loaded through the `tool_search` tool. If `tool_search` is available, the apps that are searchable by `tools_search` will be listed by it. Do not additionally call list_mcp_resources or list_mcp_resource_templates for apps. </apps_instructions><skills_instructions> ## Skills A skill is a set of instructions provided through a `SKILL.md` source. Below is the list of skills that can be used. Each entry includes a name, description, and source locator. `file` locators are on the host filesystem, `environment resource` locators are owned by an execution environment, `orchestrator resource` locators are opaque non-filesystem resources, and `custom resource` locators use their provider's access mechanism. ### Available skills - imagegen: Generate or edit raster images when the task benefits from AI-created bitmap visuals such as photos, illustrations, textures, sprites, mockups, or transparent-background cutouts. Use when Codex should create a brand-new image, transform an existing image, or derive visual variants from references, and the output should be a bitmap asset rather than repo-native code or vector. Do not use when the task is better handled by editing existing SVG/vector/code-native assets, extending an established icon or logo system, or building the visual directly in HTML/CSS/canvas. (file: /tmp/codex-home/skills/.system/imagegen/SKILL.md) - openai-docs: Use when the user asks how to build with OpenAI products or APIs, asks about Codex itself or choosing Codex surfaces, needs up-to-date official documentation with citations, help choosing the latest model for a use case, or model upgrade and prompt-upgrade guidance; use OpenAI docs MCP tools for non-Codex docs questions, use the Codex manual helper first for broad Codex self-knowledge, and restrict fallback browsing to official OpenAI domains. (file: /tmp/codex-home/skills/.system/openai-docs/SKILL.md) - plugin-creator: Create and scaffold plugin directories for Codex with a required `.codex-plugin/plugin.json`, optional plugin folders/files, valid manifest defaults, and personal-marketplace entries by default. Use when Codex needs to create a new personal plugin, add optional plugin structure, generate or update marketplace entries for plugin ordering and availability metadata, or update an existing local plugin during development with the CLI-driven cachebuster and reinstall flow. (file: /tmp/codex-home/skills/.system/plugin-creator/SKILL.md) - skill-creator: Guide for creating effective skills. This skill should be used when users want to create a new skill (or update an existing skill) that extends Codex's capabilities with specialized knowledge, workflows, or tool integrations. (file: /tmp/codex-home/skills/.system/skill-creator/SKILL.md) - skill-installer: Install Codex skills into $CODEX_HOME/skills from a curated list or a [code-host] repo path. Use when a user asks to list installable skills, install a curated skill, or install a skill from another repo (including private repos). (file: /tmp/codex-home/skills/.system/skill-installer/SKILL.md) ### How to use skills - Discovery: The list above is the skills available in this session (name + description + source locator). `file` entries live on the host filesystem, `environment resource` entries are owned by their execution environment, `orchestrator resource` entries must be accessed through `skills.list` and `skills.read`, and `custom resource` entries use their provider's access mechanism. - Trigger rules: If the user names a skill (with `$SkillName` or plain text) OR the task clearly matches a skill's description shown above, you must use that skill for that turn. Multiple mentions mean use them all. Do not carry skills across turns unless re-mentioned. - Missing/blocked: If a named skill isn't in the list or its source can't be read, say so briefly and continue with the best fallback. - How to use a skill (progressive disclosure): 1) After deciding to use a skill, the main agent must read its `SKILL.md` completely before taking task actions. For a `file` entry, open the listed path. For an `environment resource`, use the filesystem of the owning environment. For an `orchestrator resource`, call `skills.list` with `{"authority":{"kind":"orchestrator"}}`, select the matching package, and pass its `main_resource` to `skills.read`. If a read is truncated or paginated, continue until EOF. 2) When `SKILL.md` references another resource, use the same access mechanism. Resolve relative paths against a filesystem-backed skill directory. For orchestrator skills, pass the exact referenced resource identifier with the same authority and package to `skills.read`; do not treat `skill://` identifiers as filesystem paths. 3) If `SKILL.md` points to extra folders such as `references/`, use its routing instructions to identify the resources required for the task. The main agent must read each required instruction or reference file itself before acting on it. Do not delegate reading, summarizing, or interpreting skill instructions to a subagent. Subagents may still perform task work when the selected skill allows it. 4) For filesystem-backed skills, prefer running or patching provided scripts instead of retyping large code blocks. For orchestrator skills, use `skills.read` and the available tools; do not invent a local path. 5) Reuse provided assets or templates through the same source access mechanism instead of recreating them. - Coordination and sequencing: - If multiple skills apply, choose the minimal set that covers the request and state the order you'll use them. - Announce which skill(s) you're using and why (one short line). If you skip an obvious skill, say why. - Context hygiene: - Progressive disclosure applies to selecting relevant files, not partially reading a selected instruction file. Do not load unrelated references, scripts, or assets. - Avoid deep reference-chasing: prefer opening only files directly linked from `SKILL.md` unless you're blocked. - When variants exist (frameworks, providers, domains), pick only the relevant reference file(s) and note that choice. - Safety and fallback: If a skill can't be applied cleanly (missing files, unclear instructions), state the issue, pick the next-best approach, and continue. </skills_instructions>
<environment_context> <cwd>/app</cwd> <shell>bash</shell> <current_date>2026-06-20</current_date> <timezone>Etc/UTC</timezone> <filesystem><workspace_roots><root>/app</root></workspace_roots><permission_profile type="disabled"><file_system type="unrestricted" /></permission_profile></filesystem> </environment_context>
Implement `/app/dut.sv`. Define `TopModule` with this port list: `input clk, rst, cmd_valid, bit_in, scl_i, sda_i; input [1:0] cmd; output cmd_ack, busy, al, bit_out, scl_drive_low, sda_drive_low;`. Define another module and instantiate it from `TopModule`. `rst` is synchronous active high and clears outputs to 0. All outputs are registered. `cmd_ack` is a one-cycle completion pulse. Accept a command only when none is active; `cmd=0` may be accepted while idle or busy, and other commands only while `busy` is high. Illegal commands leave outputs unchanged and do not acknowledge. The line controls are open-drain: 1 pulls low, 0 releases. The command-accept edge only loads the first registered phase; it must not also consume `scl_i` or sample `sda_i` for phase completion. Because every output is registered, when a later phase says "until `scl_i` is high", the clock edge that observes high only records that fact; the next visible line-drive/ack phase appears on the following clock. Command acceptance itself is a visible registered phase: for stop, write, and read, the line-drive values loaded on the accept edge must be held through one additional full clocked setup cycle before the SCL-release phase begins. `cmd=0` starts or restarts ownership: release both lines on accept, then in following clocked wait phase keep both released until `scl_i` is high, keep SCL released while pulling SDA low for one full cycle, then pull SCL low and pulse `cmd_ack`; `busy` is set from the accept edge. `cmd=1` stops: drive both low on accept, keep both low for the following setup cycle, release SCL until `scl_i` is high, then release SDA, clear `busy`, and pulse `cmd_ack` on the following clock. `cmd=2` writes `bit_in`: on accept drive SCL low and drive SDA low for 0 or released for 1, keep those drive values for the following setup cycle, release SCL until `scl_i` is high, then pull SCL low and acknowledge on the following clock. `cmd=3` reads: on accept drive SCL low and release SDA, keep those drive values for the following setup cycle, release SCL until `scl_i` is high, sample `sda_i` on that high-SCL edge into `bit_out`, then pull SCL low and acknowledge on the following clock. `al` is sticky until reset and asserts only during start or write-1 high-SCL phases when released SDA is observed low.
I’ll inspect the workspace first so the implementation matches whatever harness or style is already present.
shell
pwd && rg --files -g '!*'
output
Chunk ID: a6d298
Wall time: 0.0000 seconds
Process exited with code 1
Original token count: 2
Output:
/app
shell
ls -la /app
output
Chunk ID: cb87ad
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 24
Output:
total 8
drwxr-xr-x 2 root root 4096 Jun 19 22:02 .
drwxr-xr-x 1 root root 4096 Jun 20 17:36 ..
The workspace is empty, so I’m creating the implementation from the timing contract in the prompt rather than adapting an existing design. The key part is the FSM needs explicit registered “recorded high” states so observing `scl_i` does not change visible line drives until the next clock.
I’m going to add `dut.sv` with a small wrapper `TopModule` and a separate registered command engine. The FSM will keep command acceptance, setup, SCL-wait observation, and completion as distinct clocked phases.
apply_patch
*** Begin Patch
*** Add File: /app/dut.sv
+module TopModule(
+    input clk,
+    input rst,
+    input cmd_valid,
+    input bit_in,
+    input scl_i,
+    input sda_i,
+    input [1:0] cmd,
+    output cmd_ack,
+    output busy,
+    output al,
+    output bit_out,
+    output scl_drive_low,
+    output sda_drive_low
+);
+
+    I2cBitCommandEngine engine (
+        .clk(clk),
+        .rst(rst),
+        .cmd_valid(cmd_valid),
+        .bit_in(bit_in),
+        .scl_i(scl_i),
+        .sda_i(sda_i),
+        .cmd(cmd),
+        .cmd_ack(cmd_ack),
+        .busy(busy),
+        .al(al),
+        .bit_out(bit_out),
+        .scl_drive_low(scl_drive_low),
+        .sda_drive_low(sda_drive_low)
+    );
+
+endmodule
+
+module I2cBitCommandEngine(
+    input logic clk,
+    input logic rst,
+    input logic cmd_valid,
+    input logic bit_in,
+    input logic scl_i,
+    input logic sda_i,
+    input logic [1:0] cmd,
+    output logic cmd_ack,
+    output logic busy,
+    output logic al,
+    output logic bit_out,
+    output logic scl_drive_low,
+    output logic sda_drive_low
+);
+
+    localparam logic [1:0] CMD_START = 2'd0;
+    localparam logic [1:0] CMD_STOP  = 2'd1;
+    localparam logic [1:0] CMD_WRITE = 2'd2;
+    localparam logic [1:0] CMD_READ  = 2'd3;
+
+    typedef enum logic [3:0] {
+        ST_IDLE,
+        ST_START_WAIT_HIGH,
+        ST_START_SDA_LOW,
+        ST_START_DONE,
+        ST_STOP_SETUP,
+        ST_STOP_WAIT_HIGH,
+        ST_STOP_DONE,
+        ST_WRITE_SETUP,
+        ST_WRITE_WAIT_HIGH,
+        ST_WRITE_DONE,
+        ST_READ_SETUP,
+        ST_READ_WAIT_HIGH,
+        ST_READ_DONE
+    } state_t;
+
+    state_t state;
+    logic write_bit;
+
+    always_ff @(posedge clk) begin
+        if (rst) begin
+            state <= ST_IDLE;
+            write_bit <= 1'b0;
+            cmd_ack <= 1'b0;
+            busy <= 1'b0;
+            al <= 1'b0;
+            bit_out <= 1'b0;
+            scl_drive_low <= 1'b0;
+            sda_drive_low <= 1'b0;
+        end else begin
+            cmd_ack <= 1'b0;
+
+            case (state)
+                ST_IDLE: begin
+                    if (cmd_valid && (cmd == CMD_START)) begin
+                        busy <= 1'b1;
+                        scl_drive_low <= 1'b0;
+                        sda_drive_low <= 1'b0;
+                        state <= ST_START_WAIT_HIGH;
+                    end else if (cmd_valid && busy && (cmd == CMD_STOP)) begin
+                        scl_drive_low <= 1'b1;
+                        sda_drive_low <= 1'b1;
+                        state <= ST_STOP_SETUP;
+                    end else if (cmd_valid && busy && (cmd == CMD_WRITE)) begin
+                        write_bit <= bit_in;
+                        scl_drive_low <= 1'b1;
+                        sda_drive_low <= ~bit_in;
+                        state <= ST_WRITE_SETUP;
+                    end else if (cmd_valid && busy && (cmd == CMD_READ)) begin
+                        scl_drive_low <= 1'b1;
+                        sda_drive_low <= 1'b0;
+                        state <= ST_READ_SETUP;
+                    end
+                end
+
+                ST_START_WAIT_HIGH: begin
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b0;
+                    if (scl_i) begin
+                        if (!sda_i) begin
+                            al <= 1'b1;
+                        end
+                        state <= ST_START_SDA_LOW;
+                    end
+                end
+
+                ST_START_SDA_LOW: begin
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b1;
+                    state <= ST_START_DONE;
+                end
+
+                ST_START_DONE: begin
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= 1'b1;
+                    cmd_ack <= 1'b1;
+                    state <= ST_IDLE;
+                end
+
+                ST_STOP_SETUP: begin
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= 1'b1;
+                    state <= ST_STOP_WAIT_HIGH;
+                end
+
+                ST_STOP_WAIT_HIGH: begin
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b1;
+                    if (scl_i) begin
+                        state <= ST_STOP_DONE;
+                    end
+                end
+
+                ST_STOP_DONE: begin
+                    busy <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b0;
+                    cmd_ack <= 1'b1;
+                    state <= ST_IDLE;
+                end
+
+                ST_WRITE_SETUP: begin
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= ~write_bit;
+                    state <= ST_WRITE_WAIT_HIGH;
+                end
+
+                ST_WRITE_WAIT_HIGH: begin
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= ~write_bit;
+                    if (scl_i) begin
+                        if (write_bit && !sda_i) begin
+                            al <= 1'b1;
+                        end
+                        state <= ST_WRITE_DONE;
+                    end
+                end
+
+                ST_WRITE_DONE: begin
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= ~write_bit;
+                    cmd_ack <= 1'b1;
+                    state <= ST_IDLE;
+                end
+
+                ST_READ_SETUP: begin
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= 1'b0;
+                    state <= ST_READ_WAIT_HIGH;
+                end
+
+                ST_READ_WAIT_HIGH: begin
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b0;
+                    if (scl_i) begin
+                        bit_out <= sda_i;
+                        state <= ST_READ_DONE;
+                    end
+                end
+
+                ST_READ_DONE: begin
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= 1'b0;
+                    cmd_ack <= 1'b1;
+                    state <= ST_IDLE;
+                end
+
+                default: begin
+                    state <= ST_IDLE;
+                end
+            endcase
+        end
+    end
+
+endmodule
*** End Patch


Exit code: 0
Wall time: 0 seconds
Output:
Success. Updated the following files:
A /app/dut.sv
The implementation is in place. I’m doing a syntax/lint pass now and will make any small fixes if the local toolchain flags SystemVerilog issues.
shell
command -v verilator
output
Chunk ID: 10a3ef
Wall time: 0.0000 seconds
Process exited with code 1
Original token count: 0
Output:
shell
command -v iverilog
output
Chunk ID: 91df66
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 5
Output:
/usr/bin/iverilog
shell
sed -n '1,260p' /app/dut.sv
output
Chunk ID: fd92b7
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 1535
Output:
module TopModule(
    input clk,
    input rst,
    input cmd_valid,
    input bit_in,
    input scl_i,
    input sda_i,
    input [1:0] cmd,
    output cmd_ack,
    output busy,
    output al,
    output bit_out,
    output scl_drive_low,
    output sda_drive_low
);

    I2cBitCommandEngine engine (
        .clk(clk),
        .rst(rst),
        .cmd_valid(cmd_valid),
        .bit_in(bit_in),
        .scl_i(scl_i),
        .sda_i(sda_i),
        .cmd(cmd),
        .cmd_ack(cmd_ack),
        .busy(busy),
        .al(al),
        .bit_out(bit_out),
        .scl_drive_low(scl_drive_low),
        .sda_drive_low(sda_drive_low)
    );

endmodule

module I2cBitCommandEngine(
    input logic clk,
    input logic rst,
    input logic cmd_valid,
    input logic bit_in,
    input logic scl_i,
    input logic sda_i,
    input logic [1:0] cmd,
    output logic cmd_ack,
    output logic busy,
    output logic al,
    output logic bit_out,
    output logic scl_drive_low,
    output logic sda_drive_low
);

    localparam logic [1:0] CMD_START = 2'd0;
    localparam logic [1:0] CMD_STOP  = 2'd1;
    localparam logic [1:0] CMD_WRITE = 2'd2;
    localparam logic [1:0] CMD_READ  = 2'd3;

    typedef enum logic [3:0] {
        ST_IDLE,
        ST_START_WAIT_HIGH,
        ST_START_SDA_LOW,
        ST_START_DONE,
        ST_STOP_SETUP,
        ST_STOP_WAIT_HIGH,
        ST_STOP_DONE,
        ST_WRITE_SETUP,
        ST_WRITE_WAIT_HIGH,
        ST_WRITE_DONE,
        ST_READ_SETUP,
        ST_READ_WAIT_HIGH,
        ST_READ_DONE
    } state_t;

    state_t state;
    logic write_bit;

    always_ff @(posedge clk) begin
        if (rst) begin
            state <= ST_IDLE;
            write_bit <= 1'b0;
            cmd_ack <= 1'b0;
            busy <= 1'b0;
            al <= 1'b0;
            bit_out <= 1'b0;
            scl_drive_low <= 1'b0;
            sda_drive_low <= 1'b0;
        end else begin
            cmd_ack <= 1'b0;

            case (state)
                ST_IDLE: begin
                    if (cmd_valid && (cmd == CMD_START)) begin
                        busy <= 1'b1;
                        scl_drive_low <= 1'b0;
                        sda_drive_low <= 1'b0;
                        state <= ST_START_WAIT_HIGH;
                    end else if (cmd_valid && busy && (cmd == CMD_STOP)) begin
                        scl_drive_low <= 1'b1;
                        sda_drive_low <= 1'b1;
                        state <= ST_STOP_SETUP;
                    end else if (cmd_valid && busy && (cmd == CMD_WRITE)) begin
                        write_bit <= bit_in;
                        scl_drive_low <= 1'b1;
                        sda_drive_low <= ~bit_in;
                        state <= ST_WRITE_SETUP;
                    end else if (cmd_valid && busy && (cmd == CMD_READ)) begin
                        scl_drive_low <= 1'b1;
                        sda_drive_low <= 1'b0;
                        state <= ST_READ_SETUP;
                    end
                end

                ST_START_WAIT_HIGH: begin
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b0;
                    if (scl_i) begin
                        if (!sda_i) begin
                            al <= 1'b1;
                        end
                        state <= ST_START_SDA_LOW;
                    end
                end

                ST_START_SDA_LOW: begin
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b1;
                    state <= ST_START_DONE;
                end

                ST_START_DONE: begin
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= 1'b1;
                    cmd_ack <= 1'b1;
                    state <= ST_IDLE;
                end

                ST_STOP_SETUP: begin
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= 1'b1;
                    state <= ST_STOP_WAIT_HIGH;
                end

                ST_STOP_WAIT_HIGH: begin
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b1;
                    if (scl_i) begin
                        state <= ST_STOP_DONE;
                    end
                end

                ST_STOP_DONE: begin
                    busy <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b0;
                    cmd_ack <= 1'b1;
                    state <= ST_IDLE;
                end

                ST_WRITE_SETUP: begin
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= ~write_bit;
                    state <= ST_WRITE_WAIT_HIGH;
                end

                ST_WRITE_WAIT_HIGH: begin
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= ~write_bit;
                    if (scl_i) begin
                        if (write_bit && !sda_i) begin
                            al <= 1'b1;
                        end
                        state <= ST_WRITE_DONE;
                    end
                end

                ST_WRITE_DONE: begin
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= ~write_bit;
                    cmd_ack <= 1'b1;
                    state <= ST_IDLE;
                end

                ST_READ_SETUP: begin
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= 1'b0;
                    state <= ST_READ_WAIT_HIGH;
                end

                ST_READ_WAIT_HIGH: begin
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b0;
                    if (scl_i) begin
                        bit_out <= sda_i;
                        state <= ST_READ_DONE;
                    end
                end

                ST_READ_DONE: begin
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= 1'b0;
                    cmd_ack <= 1'b1;
                    state <= ST_IDLE;
                end

                default: begin
                    state <= ST_IDLE;
                end
            endcase
        end
    end

endmodule
`iverilog` is available here, so I’m using that for the local compile check. Verilator is not installed in this container.
shell
iverilog -g2012 -Wall -o /tmp/dut_check /app/dut.sv
output
Chunk ID: 7ef892
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 0
Output:
The compile check passed cleanly. I’m doing one last diff read to make sure the file only contains the requested implementation.
shell
git -C /app diff -- /app/dut.sv
output
Chunk ID: 6aeb18
Wall time: 0.0000 seconds
Process exited with code 127
Original token count: 11
Output:
/bin/bash: line 1: git: command not found
shell
nl -ba /app/dut.sv | sed -n '1,240p'
output
Chunk ID: 26acd9
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 1903
Output:
     1	module TopModule(
     2	    input clk,
     3	    input rst,
     4	    input cmd_valid,
     5	    input bit_in,
     6	    input scl_i,
     7	    input sda_i,
     8	    input [1:0] cmd,
     9	    output cmd_ack,
    10	    output busy,
    11	    output al,
    12	    output bit_out,
    13	    output scl_drive_low,
    14	    output sda_drive_low
    15	);
    16	
    17	    I2cBitCommandEngine engine (
    18	        .clk(clk),
    19	        .rst(rst),
    20	        .cmd_valid(cmd_valid),
    21	        .bit_in(bit_in),
    22	        .scl_i(scl_i),
    23	        .sda_i(sda_i),
    24	        .cmd(cmd),
    25	        .cmd_ack(cmd_ack),
    26	        .busy(busy),
    27	        .al(al),
    28	        .bit_out(bit_out),
    29	        .scl_drive_low(scl_drive_low),
    30	        .sda_drive_low(sda_drive_low)
    31	    );
    32	
    33	endmodule
    34	
    35	module I2cBitCommandEngine(
    36	    input logic clk,
    37	    input logic rst,
    38	    input logic cmd_valid,
    39	    input logic bit_in,
    40	    input logic scl_i,
    41	    input logic sda_i,
    42	    input logic [1:0] cmd,
    43	    output logic cmd_ack,
    44	    output logic busy,
    45	    output logic al,
    46	    output logic bit_out,
    47	    output logic scl_drive_low,
    48	    output logic sda_drive_low
    49	);
    50	
    51	    localparam logic [1:0] CMD_START = 2'd0;
    52	    localparam logic [1:0] CMD_STOP  = 2'd1;
    53	    localparam logic [1:0] CMD_WRITE = 2'd2;
    54	    localparam logic [1:0] CMD_READ  = 2'd3;
    55	
    56	    typedef enum logic [3:0] {
    57	        ST_IDLE,
    58	        ST_START_WAIT_HIGH,
    59	        ST_START_SDA_LOW,
    60	        ST_START_DONE,
    61	        ST_STOP_SETUP,
    62	        ST_STOP_WAIT_HIGH,
    63	        ST_STOP_DONE,
    64	        ST_WRITE_SETUP,
    65	        ST_WRITE_WAIT_HIGH,
    66	        ST_WRITE_DONE,
    67	        ST_READ_SETUP,
    68	        ST_READ_WAIT_HIGH,
    69	        ST_READ_DONE
    70	    } state_t;
    71	
    72	    state_t state;
    73	    logic write_bit;
    74	
    75	    always_ff @(posedge clk) begin
    76	        if (rst) begin
    77	            state <= ST_IDLE;
    78	            write_bit <= 1'b0;
    79	            cmd_ack <= 1'b0;
    80	            busy <= 1'b0;
    81	            al <= 1'b0;
    82	            bit_out <= 1'b0;
    83	            scl_drive_low <= 1'b0;
    84	            sda_drive_low <= 1'b0;
    85	        end else begin
    86	            cmd_ack <= 1'b0;
    87	
    88	            case (state)
    89	                ST_IDLE: begin
    90	                    if (cmd_valid && (cmd == CMD_START)) begin
    91	                        busy <= 1'b1;
    92	                        scl_drive_low <= 1'b0;
    93	                        sda_drive_low <= 1'b0;
    94	                        state <= ST_START_WAIT_HIGH;
    95	                    end else if (cmd_valid && busy && (cmd == CMD_STOP)) begin
    96	                        scl_drive_low <= 1'b1;
    97	                        sda_drive_low <= 1'b1;
    98	                        state <= ST_STOP_SETUP;
    99	                    end else if (cmd_valid && busy && (cmd == CMD_WRITE)) begin
   100	                        write_bit <= bit_in;
   101	                        scl_drive_low <= 1'b1;
   102	                        sda_drive_low <= ~bit_in;
   103	                        state <= ST_WRITE_SETUP;
   104	                    end else if (cmd_valid && busy && (cmd == CMD_READ)) begin
   105	                        scl_drive_low <= 1'b1;
   106	                        sda_drive_low <= 1'b0;
   107	                        state <= ST_READ_SETUP;
   108	                    end
   109	                end
   110	
   111	                ST_START_WAIT_HIGH: begin
   112	                    scl_drive_low <= 1'b0;
   113	                    sda_drive_low <= 1'b0;
   114	                    if (scl_i) begin
   115	                        if (!sda_i) begin
   116	                            al <= 1'b1;
   117	                        end
   118	                        state <= ST_START_SDA_LOW;
   119	                    end
   120	                end
   121	
   122	                ST_START_SDA_LOW: begin
   123	                    scl_drive_low <= 1'b0;
   124	                    sda_drive_low <= 1'b1;
   125	                    state <= ST_START_DONE;
   126	                end
   127	
   128	                ST_START_DONE: begin
   129	                    scl_drive_low <= 1'b1;
   130	                    sda_drive_low <= 1'b1;
   131	                    cmd_ack <= 1'b1;
   132	                    state <= ST_IDLE;
   133	                end
   134	
   135	                ST_STOP_SETUP: begin
   136	                    scl_drive_low <= 1'b1;
   137	                    sda_drive_low <= 1'b1;
   138	                    state <= ST_STOP_WAIT_HIGH;
   139	                end
   140	
   141	                ST_STOP_WAIT_HIGH: begin
   142	                    scl_drive_low <= 1'b0;
   143	                    sda_drive_low <= 1'b1;
   144	                    if (scl_i) begin
   145	                        state <= ST_STOP_DONE;
   146	                    end
   147	                end
   148	
   149	                ST_STOP_DONE: begin
   150	                    busy <= 1'b0;
   151	                    scl_drive_low <= 1'b0;
   152	                    sda_drive_low <= 1'b0;
   153	                    cmd_ack <= 1'b1;
   154	                    state <= ST_IDLE;
   155	                end
   156	
   157	                ST_WRITE_SETUP: begin
   158	                    scl_drive_low <= 1'b1;
   159	                    sda_drive_low <= ~write_bit;
   160	                    state <= ST_WRITE_WAIT_HIGH;
   161	                end
   162	
   163	                ST_WRITE_WAIT_HIGH: begin
   164	                    scl_drive_low <= 1'b0;
   165	                    sda_drive_low <= ~write_bit;
   166	                    if (scl_i) begin
   167	                        if (write_bit && !sda_i) begin
   168	                            al <= 1'b1;
   169	                        end
   170	                        state <= ST_WRITE_DONE;
   171	                    end
   172	                end
   173	
   174	                ST_WRITE_DONE: begin
   175	                    scl_drive_low <= 1'b1;
   176	                    sda_drive_low <= ~write_bit;
   177	                    cmd_ack <= 1'b1;
   178	                    state <= ST_IDLE;
   179	                end
   180	
   181	                ST_READ_SETUP: begin
   182	                    scl_drive_low <= 1'b1;
   183	                    sda_drive_low <= 1'b0;
   184	                    state <= ST_READ_WAIT_HIGH;
   185	                end
   186	
   187	                ST_READ_WAIT_HIGH: begin
   188	                    scl_drive_low <= 1'b0;
   189	                    sda_drive_low <= 1'b0;
   190	                    if (scl_i) begin
   191	                        bit_out <= sda_i;
   192	                        state <= ST_READ_DONE;
   193	                    end
   194	                end
   195	
   196	                ST_READ_DONE: begin
   197	                    scl_drive_low <= 1'b1;
   198	                    sda_drive_low <= 1'b0;
   199	                    cmd_ack <= 1'b1;
   200	                    state <= ST_IDLE;
   201	                end
   202	
   203	                default: begin
   204	                    state <= ST_IDLE;
   205	                end
   206	            endcase
   207	        end
   208	    end
   209	
   210	endmodule
Implemented [/app/dut.sv](/app/dut.sv:1). It defines `TopModule` with the requested ports and instantiates `I2cBitCommandEngine`. The engine uses a synchronous registered FSM for start, stop, write, and read, with registered outputs, synchronous active-high reset, one-cycle `cmd_ack`, sticky `al`, and the delayed SCL-high observation behavior described. Verified with: ```bash iverilog -g2012 -Wall -o /tmp/dut_check /app/dut.sv ```
Final diff , what the agent changed

No file changes, the agent left the workspace untouched.

Verifier output , the proof behind the reward
tests/test.sh
MISMATCH_COUNTS cmd_ack=0 busy=0 al=0 bit_out=0 scl=0 sda=0
__CHIPBENCH_MISMATCH_SUMMARY__: mismatches=0 samples=2351

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_172f113c7dcc457b. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_172f113c7dcc457b · verifier authoritative; classifier explanatory.