verify: JTAG boundary-scan chain integrity (flagship)

New check_jtag_chain(System*): collects TAP pins by PinSpec.function, resolves
each to its net, and flags JtagTapIncomplete (a device missing TDI/TDO/TMS/
TCK), JtagBusUnbridged (TMS or TCK not common to every TAP device), and
JtagChainBreak (dangling TDO/TDI, chain fan-out, or not a single head->tail
daisy chain). Surfaced as a pass in `verify`; AnomalyKind extended. Covered by
test_bsdl_check (healthy chain, broken chain + split bus, incomplete TAP).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/system/analysis.cpp

@@ -26,6 +26,9 @@ const char *anomaly_kind_name(AnomalyKind k) {
     case AnomalyKind::DriveContention: return "drive-contention";
     case AnomalyKind::UndrivenNet:     return "undriven-net";
     case AnomalyKind::NcWired:         return "nc-wired";
+    case AnomalyKind::JtagTapIncomplete: return "jtag-tap-incomplete";
+    case AnomalyKind::JtagChainBreak:    return "jtag-chain-break";
+    case AnomalyKind::JtagBusUnbridged:  return "jtag-bus-unbridged";
     }
     return "?";
 }

src/system/analysis.hpp

@@ -34,6 +34,9 @@ enum class AnomalyKind {
     DriveContention, ///< A net has ≥2 push-pull output (Out) drivers.
     UndrivenNet,     ///< A net has input(s) but no driver (Out/Bidir/Power).
     NcWired,         ///< A no-connect pin is wired onto a multi-pin net.
+    JtagTapIncomplete, ///< A TAP device is missing one of TDI/TDO/TMS/TCK.
+    JtagChainBreak,    ///< The TDO→TDI daisy chain is broken / not a single path.
+    JtagBusUnbridged,  ///< TMS or TCK is not common to all TAP devices.
 };
 
 struct Anomaly {

src/system/bsdl_check.cpp

@@ -9,10 +9,18 @@
 #include "system.hpp"
 
 #include <string>
+#include <unordered_map>
+#include <utility>
 #include <vector>
 
 namespace {
 
+std::string part_label(const Part *p)
+{
+    std::string mod = (p && p->prnt) ? p->prnt->name : std::string("?");
+    return mod + "/" + (p ? p->name : std::string("?"));
+}
+
 std::string pin_label(const Pin *p)
 {
     std::string part = (p && p->prnt) ? p->prnt->name : std::string("?");
@@ -109,3 +117,160 @@ std::vector<Anomaly> check_pin_specs(System *sys)
 
     return out;
 }
+
+std::vector<Anomaly> check_jtag_chain(System *sys)
+{
+    std::vector<Anomaly> out;
+    if (!sys)
+        return out;
+
+    // Map every pin to the index of the net it sits on.
+    std::vector<Net> nets = compute_all_nets(sys);
+    std::unordered_map<Pin *, int> net_of;
+    for (size_t i = 0; i < nets.size(); ++i)
+        for (auto &mp : nets[i].members)
+            for (auto &kv : *mp.second)
+                net_of[kv.second] = (int)i;
+    auto net_id = [&](Pin *p) -> int {
+        if (!p) return -1;
+        auto it = net_of.find(p);
+        return it == net_of.end() ? -1 : it->second;
+    };
+
+    // Collect TAP devices: any part carrying ≥1 pin with a TAP function.
+    struct Tap {
+        Part *part = nullptr;
+        Pin *tdi = nullptr, *tdo = nullptr, *tms = nullptr, *tck = nullptr, *trst = nullptr;
+    };
+    std::vector<Tap> taps;
+    for (auto &mkv : *sys->modules())
+        for (auto &pkv : *mkv.second) {
+            Tap t;
+            t.part = pkv.second;
+            bool any = false;
+            for (auto &nkv : *t.part) {
+                Pin *pin = nkv.second;
+                switch (pin->spec.function) {
+                case PinFunction::JtagTdi:  t.tdi = pin;  any = true; break;
+                case PinFunction::JtagTdo:  t.tdo = pin;  any = true; break;
+                case PinFunction::JtagTms:  t.tms = pin;  any = true; break;
+                case PinFunction::JtagTck:  t.tck = pin;  any = true; break;
+                case PinFunction::JtagTrst: t.trst = pin; any = true; break;
+                default: break;
+                }
+            }
+            if (any) taps.push_back(t);
+        }
+
+    if (taps.empty())
+        return out;
+
+    // (1) every TAP device needs the four mandatory signals.
+    for (const Tap &t : taps) {
+        std::string miss;
+        auto need = [&](Pin *p, const char *n) {
+            if (!p) miss += (miss.empty() ? "" : ", ") + std::string(n);
+        };
+        need(t.tdi, "TDI"); need(t.tdo, "TDO"); need(t.tms, "TMS"); need(t.tck, "TCK");
+        if (!miss.empty()) {
+            Anomaly a;
+            a.kind = AnomalyKind::JtagTapIncomplete;
+            a.module = t.part ? t.part->prnt : nullptr;
+            a.message = part_label(t.part) + ": incomplete TAP, missing " + miss;
+            out.push_back(std::move(a));
+        }
+    }
+
+    // (2) TMS and TCK must each be one common net across all TAP devices.
+    auto check_bus = [&](const char *name, const std::vector<std::pair<Part *, Pin *>> &pins) {
+        if (pins.size() < 2)
+            return;
+        int ref = -1;
+        for (const auto &pp : pins) {
+            int n = net_id(pp.second);
+            if (n >= 0) { ref = n; break; }
+        }
+        if (ref < 0) {
+            Anomaly a;
+            a.kind = AnomalyKind::JtagBusUnbridged;
+            a.message = std::string(name) + ": no TAP device has a connected " + name;
+            out.push_back(std::move(a));
+            return;
+        }
+        std::string off;
+        for (const auto &pp : pins)
+            if (net_id(pp.second) != ref)
+                off += (off.empty() ? "" : ", ") + part_label(pp.first);
+        if (!off.empty()) {
+            Anomaly a;
+            a.kind = AnomalyKind::JtagBusUnbridged;
+            a.message = std::string(name) + " is not common to all TAP devices (off-bus: "
+                      + off + ")";
+            out.push_back(std::move(a));
+        }
+    };
+    std::vector<std::pair<Part *, Pin *>> tms_pins, tck_pins;
+    for (const Tap &t : taps) {
+        if (t.tms) tms_pins.push_back({t.part, t.tms});
+        if (t.tck) tck_pins.push_back({t.part, t.tck});
+    }
+    check_bus("TMS", tms_pins);
+    check_bus("TCK", tck_pins);
+
+    // (3) TDO→TDI daisy chain: a link is two devices sharing a net (A.tdo, B.tdi).
+    const int n = (int)taps.size();
+    std::vector<int> downstream(n, 0), upstream(n, 0);
+    for (int i = 0; i < n; ++i) {
+        if (taps[i].tdo && net_id(taps[i].tdo) < 0) {
+            Anomaly a;
+            a.kind = AnomalyKind::JtagChainBreak;
+            a.module = taps[i].part ? taps[i].part->prnt : nullptr;
+            a.message = part_label(taps[i].part) + "/TDO is not connected to any net";
+            out.push_back(std::move(a));
+        }
+        if (taps[i].tdi && net_id(taps[i].tdi) < 0) {
+            Anomaly a;
+            a.kind = AnomalyKind::JtagChainBreak;
+            a.module = taps[i].part ? taps[i].part->prnt : nullptr;
+            a.message = part_label(taps[i].part) + "/TDI is not connected to any net";
+            out.push_back(std::move(a));
+        }
+    }
+    for (int i = 0; i < n; ++i)
+        for (int j = 0; j < n; ++j) {
+            if (i == j) continue;
+            int a = net_id(taps[i].tdo), b = net_id(taps[j].tdi);
+            if (a >= 0 && a == b) { ++downstream[i]; ++upstream[j]; }
+        }
+    int heads = 0, tails = 0;
+    for (int i = 0; i < n; ++i) {
+        if (downstream[i] > 1) {
+            Anomaly a;
+            a.kind = AnomalyKind::JtagChainBreak;
+            a.module = taps[i].part ? taps[i].part->prnt : nullptr;
+            a.message = part_label(taps[i].part) + "/TDO drives "
+                      + std::to_string(downstream[i]) + " TDIs (chain fan-out)";
+            out.push_back(std::move(a));
+        }
+        if (upstream[i] > 1) {
+            Anomaly a;
+            a.kind = AnomalyKind::JtagChainBreak;
+            a.module = taps[i].part ? taps[i].part->prnt : nullptr;
+            a.message = part_label(taps[i].part) + "/TDI is driven by "
+                      + std::to_string(upstream[i]) + " TDOs";
+            out.push_back(std::move(a));
+        }
+        if (taps[i].tdi && net_id(taps[i].tdi) >= 0 && upstream[i] == 0) ++heads;
+        if (taps[i].tdo && net_id(taps[i].tdo) >= 0 && downstream[i] == 0) ++tails;
+    }
+    if (n > 1 && (heads != 1 || tails != 1)) {
+        Anomaly a;
+        a.kind = AnomalyKind::JtagChainBreak;
+        a.message = "JTAG chain is not a single daisy chain: " + std::to_string(heads)
+                  + " head(s), " + std::to_string(tails) + " tail(s) over "
+                  + std::to_string(n) + " TAP device(s)";
+        out.push_back(std::move(a));
+    }
+
+    return out;
+}

src/system/bsdl_check.hpp

@@ -16,4 +16,13 @@ class System;
 // un-modelled parts).
 std::vector<Anomaly> check_pin_specs(System *sys);
 
+// JTAG boundary-scan chain integrity, using pins whose PinSpec.function is a TAP
+// role (JtagTdi/Tdo/Tms/Tck/Trst). Resolves each TAP pin to its net and checks:
+//   - JtagTapIncomplete : a TAP device missing TDI/TDO/TMS/TCK;
+//   - JtagBusUnbridged  : TMS or TCK not common to every TAP device;
+//   - JtagChainBreak    : the TDO→TDI daisy chain dangles, fans out, or is not a
+//                         single path (≠1 head / ≠1 tail).
+// Empty when the system has no TAP pins.
+std::vector<Anomaly> check_jtag_chain(System *sys);
+
 #endif // _BSDL_CHECK_HPP_

src/tui/commands.cpp

@@ -304,6 +304,13 @@ void Tui::RegisterCommands() {
             Print("  [" + std::string(anomaly_kind_name(a.kind)) + "] " + a.message);
         Print("verify: " + std::to_string(pin_anoms.size())
               + " model-driven pin anomaly(ies).");
+
+        // JTAG boundary-scan chain integrity (TAP pins → nets).
+        auto jtag_anoms = check_jtag_chain(sys.get());
+        for (const auto &a : jtag_anoms)
+            Print("  [" + std::string(anomaly_kind_name(a.kind)) + "] " + a.message);
+        Print("verify: " + std::to_string(jtag_anoms.size())
+              + " JTAG chain anomaly(ies).");
     }, true,
        "check pin roles, bridged-net consistency, and model-driven pin specs (contention/undriven/NC)" };