#0');
+ expect(description).toContain('sampled values');
+ expect(description).not.toMatch(/Mox|WASM|Mox's|commit|receipt|\/var\/tmp|fleet|census/i);
+ });
+
+ it('keeps the starter and solution distinct and binds both refdiff receipts', () => {
+ expect(starter).toContain('input sig;');
+ expect(starter).not.toContain('input #0 sig;');
+ expect(solution).toContain('input #0 sig;');
+
+ for (const [file, expectedCategory] of [
+ ['starter-refdiff.json', 'both_fail'],
+ ['solution-refdiff.json', 'both_pass'],
+ ]) {
+ const sourceName = file.startsWith('starter') ? 'clocking_sampler.sv' : 'clocking_sampler.sol.sv';
+ const source = readFileSync(path.join(lessonDir, sourceName));
+ const receipt = JSON.parse(
+ readFileSync(path.join(root, 'artifacts/tutorial/clocking-sampler-retention', file), 'utf8')
+ );
+ expect(receipt.category).toBe(expectedCategory);
+ expect(receipt.sha256).toBe(createHash('sha256').update(source).digest('hex'));
+ }
+ });
+});
diff --git a/src/lessons/curriculum-integrity.test.js b/src/lessons/curriculum-integrity.test.js
index 12fe646..e6fa62a 100644
--- a/src/lessons/curriculum-integrity.test.js
+++ b/src/lessons/curriculum-integrity.test.js
@@ -10,7 +10,6 @@ const removedStatusLessons = [
'sv/nested-child-input',
'sv/sequential-udp-init',
'sv/compile-mode-status',
- 'sv/clocking-sampler-retention',
'sv/protected-envelope-boundary',
'sv/virtual-provider-closure',
'sv/wide-readmem',
diff --git a/src/lessons/index.js b/src/lessons/index.js
index 65f1261..2a8d8c8 100644
--- a/src/lessons/index.js
+++ b/src/lessons/index.js
@@ -78,6 +78,7 @@ export const parts = [
chapters: [
{ title: 'Introduction', lessons: [L('sv/welcome'), L('sv/modules-and-ports'), L('sv/data-types'), L('sv/always-comb')] },
{ title: 'Sequential Logic', lessons: [L('sv/events'), L('sv/always-ff'), L('sv/counter')] },
+ { title: 'Clocking Blocks', lessons: [L('sv/clocking-sampler-retention')] },
{ title: 'Data Types', lessons: [L('sv/parameters'), L('sv/packed-structs')] },
{ title: 'State Machines', lessons: [L('sv/enums')] },
{ title: 'Covergroups', lessons: [L('sv/covergroup-basics'), L('sv/coverpoint-bins'), L('sv/cross-coverage')] },
diff --git a/src/lessons/meta.js b/src/lessons/meta.js
index 3e000d4..2987e97 100644
--- a/src/lessons/meta.js
+++ b/src/lessons/meta.js
@@ -10,6 +10,7 @@ export default {
'sv/events': { title: 'Events', focus: '/src/event_sync.sv', top: 'event_sync' },
'sv/always-ff': { title: 'Flip-Flops with always_ff', focus: '/src/sram_core.sv' },
'sv/counter': { title: 'Up-Counter', focus: '/src/counter.sv' },
+ 'sv/clocking-sampler-retention': { title: 'Clocking Sampler Retention', focus: '/src/clocking_sampler.sv', top: 'tb' },
'sv/parameters': { title: 'Parameters', focus: '/src/sram.sv' },
'sv/packed-structs': { title: 'Packed Structs', focus: '/src/mem_cmd.sv' },
'sv/interfaces': { title: 'Interfaces', focus: '/src/mem_if.sv' },
diff --git a/src/lessons/receipt-matrix.test.js b/src/lessons/receipt-matrix.test.js
index 94d4342..9b58fdd 100644
--- a/src/lessons/receipt-matrix.test.js
+++ b/src/lessons/receipt-matrix.test.js
@@ -6,6 +6,7 @@ import meta from './meta.js';
const root = path.resolve(process.cwd());
const receiptDir = path.join(root, 'artifacts/tutorial/receipts');
const missingDir = path.join(receiptDir, '20261001-missing');
+const capabilityReceiptSlugs = ['sv/clocking-sampler-retention'];
function genericReceiptSlugs() {
return readdirSync(receiptDir)
@@ -19,6 +20,9 @@ describe('tutorial receipt coverage', () => {
const matrix = JSON.parse(readFileSync(path.join(missingDir, 'matrix.json'), 'utf8'));
const covered = new Set([
...genericReceiptSlugs(),
+ ...capabilityReceiptSlugs.filter((slug) =>
+ existsSync(path.join(root, 'artifacts/tutorial/clocking-sampler-retention/solution-refdiff.json'))
+ ),
...matrix.entries.map((entry) => entry.slug)
]);
expect([...covered].sort()).toEqual(Object.keys(meta).sort());
diff --git a/src/lessons/sv/clocking-sampler-retention/clocking_sampler.sol.sv b/src/lessons/sv/clocking-sampler-retention/clocking_sampler.sol.sv
new file mode 100644
index 0000000..4a885b9
--- /dev/null
+++ b/src/lessons/sv/clocking-sampler-retention/clocking_sampler.sol.sv
@@ -0,0 +1,53 @@
+module tb;
+ logic clk = 0;
+ logic [7:0] sig = 8'hAA;
+ bit reactive_done = 0;
+
+ clocking cb @(posedge clk);
+ input #0 sig;
+ endclocking
+
+ always #5 clk = ~clk;
+ always @(posedge clk) sig = 8'hBB;
+ reactive_writer writer(.clk(clk));
+
+ initial begin
+ @(cb);
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: first sample=%h", cb.sig);
+ $finish;
+ end
+ wait (reactive_done);
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: same-slot sample=%h", cb.sig);
+ $finish;
+ end
+ #1;
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: retained sample=%h", cb.sig);
+ $finish;
+ end
+ #5;
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: negedge sample=%h", cb.sig);
+ $finish;
+ end
+ @(cb);
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: resample=%h", cb.sig);
+ $finish;
+ end
+ $display("PASS: clocking sample retained=%h", cb.sig);
+ $finish;
+ end
+endmodule
+
+program reactive_writer(input logic clk);
+ initial begin
+ @(posedge clk);
+ tb.sig = 8'hCC;
+ #0;
+ tb.reactive_done = 1;
+ #100;
+ end
+endprogram
diff --git a/src/lessons/sv/clocking-sampler-retention/clocking_sampler.sv b/src/lessons/sv/clocking-sampler-retention/clocking_sampler.sv
new file mode 100644
index 0000000..b6b0532
--- /dev/null
+++ b/src/lessons/sv/clocking-sampler-retention/clocking_sampler.sv
@@ -0,0 +1,53 @@
+module tb;
+ logic clk = 0;
+ logic [7:0] sig = 8'hAA;
+ bit reactive_done = 0;
+
+ clocking cb @(posedge clk);
+ input sig;
+ endclocking
+
+ always #5 clk = ~clk;
+ always @(posedge clk) sig = 8'hBB;
+ reactive_writer writer(.clk(clk));
+
+ initial begin
+ @(cb);
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: first sample=%h", cb.sig);
+ $finish;
+ end
+ wait (reactive_done);
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: same-slot sample=%h", cb.sig);
+ $finish;
+ end
+ #1;
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: retained sample=%h", cb.sig);
+ $finish;
+ end
+ #5;
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: negedge sample=%h", cb.sig);
+ $finish;
+ end
+ @(cb);
+ if (cb.sig !== 8'hBB) begin
+ $display("FAIL: resample=%h", cb.sig);
+ $finish;
+ end
+ $display("PASS: clocking sample retained=%h", cb.sig);
+ $finish;
+ end
+endmodule
+
+program reactive_writer(input logic clk);
+ initial begin
+ @(posedge clk);
+ tb.sig = 8'hCC;
+ #0;
+ tb.reactive_done = 1;
+ #100;
+ end
+endprogram
diff --git a/src/lessons/sv/clocking-sampler-retention/description.html b/src/lessons/sv/clocking-sampler-retention/description.html
new file mode 100644
index 0000000..c879ca3
--- /dev/null
+++ b/src/lessons/sv/clocking-sampler-retention/description.html
@@ -0,0 +1,14 @@
+A clocking block gives a testbench a named clock event and a sampled view of its input signals. The input skew controls when each signal is sampled relative to that event.
+ +Add an explicit #0 input skew to cb.sig. The testbench writes BB in an Active-region process, then writes CC after the clocking event has published its sample. The correct solution observes BB at the first event, keeps that sampled value through the same time slot and the following negedge, and samples BB again at the next positive edge.
clocking cb @(posedge clk); + input #0 sig; +endclocking+ +
Without an explicit input skew, the default is 1step, so the input is sampled immediately before the corresponding clock edge. With an explicit #0, the input is sampled in the Observed region. The clocking-block event is triggered after the sampled values are updated, and a clocking input keeps the value from its most recent clocking event.
+ +IEEE 1800-2023 §14.3 defines the default
1stepinput skew. §14.4 defines sampling relative to the clock event and specifies that an explicit#0input skew samples in the Observed region. §14.13 specifies that the updated sampled values are available before the clocking-block event triggers and that a#0input is not resampled during same-slot Active re-entry unless a new clocking event occurs.
Open clocking_sampler.sv and add the skew. The passing solution prints PASS: clocking sample retained=bb.