800B PDO variant + long-term stability evidence + analysis docs

- twin_layout_blob_sized generalized: multi-entry TwinCAT line format (1 real @240bit + N continuation + remainder entry); 1024B path kept byte-identical; 800B = 27 entries verified on hardware - 800B constants (PAYLOAD/SM 800), deployed as el6695_rt_800b - 10-min + 5h stability runs: 18M cycles, zero errors, zero mismatches, PLC nMismatch frozen over the whole run (monitor_5h.csv evidence) - docs: 800B plan/design/verification/test-report chapters, jitter analysis (NFS rootfs stall primary cause), D2000 dev plan - scripts: 800B deploy/relink/verify, mismatch-delta, 5h monitor
2026-08-06 01:10:50 +08:00 · 2026-08-06 01:10:50 +08:00 · f0163d8d70
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--- a/docs/800b-pdo-plan.md
+++ b/docs/800b-pdo-plan.md
@ -0,0 +1,124 @@
+# EL6695 PDO 扩展至 800 字节 — 方案文档
+
+> **版本**: 1.0
+> **日期**: 2026-07-27
+> **状态**: 待评审
+> **前置文档**: `8b-bridge-design.md`(8B 实现)、`500us-latency-plan.md`(延迟优化)
+
+---
+
+## 1. 目标
+
+在现有 8B 工程基础上,新建 **800 字节 PDO** 变体工程 `TwinCAT_EL6695_Primary_800B`,实现 TwinCAT ↔ J1900 双向 800B/周期数据交换,并保持逐字节可验证性。
+
+选型说明:800B 介于 8B(验证通路)与 1024B(ESI 默认上限)之间,可作为实际应用的带宽档位;同时验证任意尺寸的映射 blob 生成规则。
+
+---
+
+## 2. 关键技术点(复用既有经验)
+
+| # | 经验 | 应用到 800B |
+|---|---|---|
+| 1 | 链接必须整数组(`LinkVariables`) | 同 8B,PLC 数组与 PDO 条目同类型同尺寸 |
+| 2 | 类型 GUID 必须复用 PLC 构建生成的随机 GUID | 先建 PLC `ARRAY[0..799]`,构建取 GUID 填 PDO 条目 |
+| 3 | SM3 不挂 0x1A01 诊断 PDO,否则设备报 `size not allowed` | SM3 纯 800B,不含诊断(若含诊断则需 802B) |
+| 4 | EL6695 固件按 PDO 赋值总和校验 SM 长度 | SM2=SM3=800(0x0320),两侧一致 |
+| 5 | 映射 blob 须为 TwinCAT 行格式(240bit 条目 + 余量) | 见 §3 数学 |
+| 6 | 先激活 TwinCAT,再启动 J1900 ticker(同一会话) | 部署顺序不变 |
+
+---
+
+## 3. PDO 映射 blob 数学(800B)
+
+EL6695 固件要求映射为 TwinCAT 行格式:真实对象条目 @240bit + 若干 0x0000:00 延续条目,总位数 = payload 位数。
+
+```
+800 B = 6400 bit = 26 × 240 bit + 160 bit
+blob = [条目数=27 (u16 LE)]
+     + [240, 1, obj_lo, obj_hi]   (真实对象 0x6000/0x7000 子索引1)
+     + 25 × [240, 0, 0, 0]        (延续)
+     + 1 × [160, 0, 0, 0]         (余量延续)
+```
+
+`bridge.rs` 的 `twin_layout_blob_sized` 需泛化:`payload_bytes ≤ 30` 走单条目;否则按 `ceil` 生成多条目(1 真实 + (n-2) 延续 + 1 余量延续),1024B 时退化为现有 35 条目格式(字节级兼容已验证)。
+
+---
+
+## 4. 工程结构
+
+```
+twincat3-auto-cli/
+├─ TwinCAT_EL6695_Primary\        (8B, 不动)
+├─ TwinCAT_EL6695_Primary_2kHz\   (2kHz, 不动)
+├─ TwinCAT_EL6695_Primary_4kHz\   (4kHz, 不动)
+└─ TwinCAT_EL6695_Primary_800B\   (新建, 本方案)
+```
+
+J1900 二进制: `/root/gateway/el6695_rt_800b`(新构建,旧的全部保留)。
+
+---
+
+## 5. 实施步骤
+
+### 5.1 TwinCAT 侧(副本工程)
+
+| 步骤 | 内容 |
+|---|---|
+| 1 | robocopy 复制 `TwinCAT_EL6695_Primary` → `_800B`;修 sln 为相对路径(防绝对路径 bug) |
+| 2 | PLC: `GVL_Sync.aIn1/aOut1` → `ARRAY[0..799] OF BYTE`;MAIN 协议改 800B 布局(§6) |
+| 3 | 构建 PLC → 从 tsproj 取 `ARRAY [0..799]` 的随机 GUID |
+| 4 | tsproj PDO 条目(0x1608/0x1A08)类型替换为该 GUID 的 `ARRAY [0..799] OF BYTE` |
+| 5 | SM2 记录: `001c200364...`(len=0x0320=800);SM3 记录: `008e200320...`(len=800),0x1A01 仍不挂 SM3 |
+| 6 | `tc-relink.ps1` 整数组重建链接;部署激活;验证 _Boot tszip 中 SM2/SM3=800 |
+
+### 5.2 J1900 侧
+
+| 步骤 | 内容 |
+|---|---|
+| 1 | `twin_layout_blob_sized` 泛化为多条目(§3) |
+| 2 | 常量: `PAYLOAD_LEN=SM_TX_LEN=SM_RX_LEN=SM_RX_PLD_LEN=800` |
+| 3 | SM 长度写 800;FMMU len 写 800 |
+| 4 | ticker 走 1KB 式协议路径(f(x)=x·7+3 + 图案回显 + 时间戳字段),现有编译期守卫 `PAYLOAD_LEN>=256/280` 自动生效 |
+| 5 | 交叉编译(rust-lld)→ scp 为 `el6695_rt_800b` |
+
+### 5.3 数据协议(800B 布局)
+
+| 偏移 | 内容 | 方向 |
+|---|---|---|
+| [0..7] | TwinCAT `nCycles`(ULINT) → J1900 回 `nCycles*7+3` | 双向 |
+| [8..15] | J1900 本地周期号 | J→T |
+| [16..799] | 逐字节图案 `(nCycles + i) mod 256`,J1900 原样回显 | 双向 |
+| [264..267] | J1900 周期抖动 ns | J→T |
+| [268..271] | J1900 图案失配计数 | J→T |
+| [272..279] | J1900 回存的原始 tc_seq | J→T |
+
+TwinCAT 校验(复用 1KB 逻辑):从 `nProcessedSeq` 反推原始 seq → 按 seq 重建预期图案逐字节比对 [16..799] → `bSync`;RTT = nCycles − nReturnedSeq。
+
+### 5.4 验证
+
+1. J1900 日志:SM2/SM3 len=800、OP、stale=0%、mism=0;
+2. TwinCAT ADS: `bSync=True`、`aIn1` 非零字节数 ≈ 784(图案区)、RTT 稳定;
+3. 逐字节证据:抽 [16..799] 中多个偏移核对 `(seq+i) mod 256`;
+4. 连续 10 分钟:nMismatch 零增长、tx/rx 零错误;
+5. 频率:保持 1kHz(带宽目标,不引入 2k/4k 变量)。
+
+---
+
+## 6. 风险与注意点
+
+| # | 风险 | 缓解 |
+|---|---|---|
+| R1 | 多条目 blob 被固件拒绝(余量条目不认) | 先用 verify 模式观察 AL 状态码;备选:全部按 240bit 进位到 27×240(6480bit,多 80bit 填 0) |
+| R2 | 800B 时 SM 长度设备校验失败 | 事件日志看 `min/max size`;按报告值对齐 |
+| R3 | PLC 构建后 tsproj 类型 GUID 抓取失败 | 构建后 rg 校验 GUID 存在再替换 |
+| R4 | 1kHz 下 800B 帧对 E-bus 其他端子无影响 | 既有端子已在 1kHz 验证过,800B 增量小 |
+
+## 7. 工时估计
+
+约 2–3 小时(含一次失败重试余量):tsproj 手术 30min、PLC 30min、J1900 blob 泛化+构建 40min、联调验证 40min。
+
+## 8. 修订历史
+
+| 日期 | 内容 |
+|---|---|
+| 2026-07-27 | 初版方案 |
--- a/docs/8b-bridge-design.md
+++ b/docs/8b-bridge-design.md
@ -1,6 +1,6 @@
 # EL6695 桥接 8 字节双向实时通讯 — 设计文档

-> **版本**: 1.0
+> **版本**: 1.1(新增 §8 800B 变体)
 > **日期**: 2026-07-27
 > **状态**: 已实现并验证通过
 > **前置文档**: `1kb-verification-progress.md`(1KB 版本演进史)
@ -224,3 +224,64 @@ scp -J tonycao@192.168.58.8 target/x86_64-unknown-linux-musl/release/el6695-rt `
 1. **无诊断 PDO**: 8B 配置不含 "External device not connected" 等状态位。若需要,须在 SM3 同时赋值 0x1A01+0x1A08 并保持 SM3=10(TwinCAT 侧重算逻辑需相应修正)。
 2. **延迟**: 往返固定 4 个 PLC 周期(≈4ms @1kHz),未做 DC 同步优化。
 3. **尺寸扩展**: 本设计的修改方法(GUID 类型 + SM 记录 + J1900 常量)适用于任意 ≤240bit 的单条目尺寸;更大尺寸需在 `twin_layout_blob_sized` 中恢复多条目延续格式。
+
+---
+
+## 8. 800B 变体(已实现并验证)
+
+在 8B 验证通路基础上,扩展出 800 字节 PDO 工程 `TwinCAT_EL6695_Primary_800B`,作为实际应用的带宽档位,并验证了任意尺寸的映射 blob 生成规则。
+
+### 8.1 与 8B 设计的差异
+
+| 项 | 8B | 800B |
+|---|---|---|
+| PDO 条目类型 | `ARRAY [0..7] OF BYTE` | `ARRAY [0..799] OF BYTE`(GUID `{7D10FDFE-13E3-A012-D822-BE30F7D36D23}`,PLC 构建生成) |
+| SM2/SM3 长度 | 8 / 8 | **800 / 800**(0x0320) |
+| 0x1A01 诊断 PDO | 不挂 SM3 | 同左(沿用,否则设备报 `size not allowed`) |
+| 映射 blob | 单条目 64bit | **27 条目**(见 §8.2) |
+| 数据协议 | 每字节 XOR 0x5A + 历史环 | seq + f(x)=x·7+3 + 逐字节图案 + 反推校验(类 1KB) |
+| 周期 | 1kHz(基线) | 1kHz |
+
+### 8.2 多条目映射 blob 生成规则
+
+EL6695 固件接受 TwinCAT 行格式:1 真实对象条目 @240bit + N 延续条目(0x0000:00)@240bit + 1 余量延续条目。
+
+```
+800 B = 6400 bit = 26 × 240 bit + 160 bit
+blob = [27 (u16 LE)]
+     + [240, 1, obj_lo, obj_hi]   真实对象 (0x6000:01 / 0x7000:01)
+     + 25 × [240, 0, 0, 0]        延续
+     + 1 × [160, 0, 0, 0]         余量延续
+```
+
+`twin_layout_blob_sized(obj, n)` 泛化实现:≤240bit 单条目;>240bit 按上式多条目;1024B 特判保持原 35 条目格式(字节级兼容)。
+
+### 8.3 800B 数据布局
+
+| 偏移 | 内容 | 方向 |
+|---|---|---|
+| [0..7] | TwinCAT `nCycles` → J1900 回 `nCycles*7+3` | 双向 |
+| [8..15] | J1900 本地周期号 | J→T |
+| [16..263] | 逐字节图案 `(nCycles+i) mod 256`,J1900 原样回显 | 双向 |
+| [264..267] | J1900 周期抖动 ns | J→T |
+| [268..271] | J1900 图案失配计数 | J→T |
+| [272..279] | J1900 回存的原始 tc_seq | J→T |
+| [280..799] | 逐字节图案(同上) | 双向 |
+
+**设计要点:图案区必须避开 [264..279] 统计字段**——首版实现按 [16..799] 连续图案,J1900 统计字段覆盖 16 字节导致 PLC 每周期 16 字节失配。
+
+### 8.4 新增陷阱(800B 实测)
+
+| # | 现象 | 根因 | 解决 |
+|---|---|---|---|
+| 8 | 激活时 EL6695 SAFEOP 失败,AL 状态码 0x0003 | **激活与 J1900 ticker 会话并发**:relink 激活时 ticker 正在跑,桥两侧主站会话冲突 | 激活必须在 J1900 空闲时进行;失败后空载重新激活即恢复 |
+| 9 | 数据通但 PLC bSync=False,每周期固定 16 字节失配 | 图案区 [16..799] 与 J1900 统计字段 [264..279] 重叠 | 图案区改为 [16..263]+[280..799](见 §8.3) |
+
+### 8.5 800B 实测性能
+
+| 指标 | 值 |
+|---|---|
+| J1900 exec(800B,同步写) | 均值 384µs / p99 400µs |
+| FPRD(读 800B) | 均值 139µs / p99 156µs(8B 时为 71µs) |
+| FPWR(写 800B) | 均值 244µs / p99 260µs(与 8B 基本持平) |
+| 桥接 RTT(1kHz) | 4 周期(lag=4,同 8B/1KB 结构) |
--- a/docs/8b-test-report.md
+++ b/docs/8b-test-report.md
@ -1,6 +1,6 @@
 # EL6695 8B 双向通讯 — 测试文档

-> **版本**: 1.0
+> **版本**: 1.1(新增 §8 800B 测试)
 > **日期**: 2026-07-27
 > **结论**: ✅ 全部通过
 > **配套文档**: `8b-bridge-design.md`、`8b-verification-methodology.md`
@ -172,3 +172,60 @@ Copy-Item "C:\Users\tonycao\work\twincat3-auto-cli\TwinCAT_EL6695_Primary\TwinCA
 | 日期 | 内容 |
 |---|---|
 | 2026-07-27 | 初版:8B 双向交换全部测试通过 |
+
+---
+
+## 8. 800B 变体测试(2026-07-28)
+
+### 8.1 环境差异
+
+| 项 | 值 |
+|---|---|
+| TwinCAT 工程 | `TwinCAT_EL6695_Primary_800B`(1kHz 任务) |
+| PDO 尺寸 | 800B(SM2/SM3 = 0x0320) |
+| J1900 二进制 | `/root/gateway/el6695_rt_800b` |
+| 校验脚本 | `scripts/tc-ads-verify-800b.ps1`、`tc-ads-mismatch-delta.ps1`、`tc-relink-800b.ps1`、`tc-deploy-retry-800b.ps1` |
+
+### 8.2 配置确认(激活后 _Boot tszip)
+
+```
+SM2: 001c200364...  (start=0x1C00 len=0x0320=800 ✓ 保留)
+SM3: 008e200320...  (start=0x8E00 len=0x0320=800 ✓ 保留)
+PDO 条目: ARRAY [0..799] OF BYTE (GUID {7D10FDFE-13E3-A012-D822-BE30F7D36D23})
+事件日志: 无 EL6695 错误
+```
+
+### 8.3 功能验证
+
+| 项 | 结果 |
+|---|---|
+| J1900 映射 blob | 27 条目(26×240+160bit)被固件接受,SAFEOP/OP 通过 |
+| 处理证明 | `proc = raw*7+3` 逐样本精确(如 107636 → 753455) |
+| PLC 校验 | bSync=True,lag=4 |
+| 图案覆盖 | aIn1 非零 775–776/800;[16..263]+[280..799] 逐字节 `(seq+i)%256` 抽查全对 |
+
+### 8.4 10 分钟稳定性(600,000 周期)
+
+| 指标 | 结果 |
+|---|---|
+| 周期完整 | 600000 周期 / 600.0s,零丢失 |
+| 传输错误 | tx_err=0, rx_err=0 |
+| J1900 图案失配 | mism=0 |
+| PLC nMismatch | 295s 运行窗口零增长;90s 确认测试 delta=0 |
+| stale | 2999 周期(0.5%) |
+| 周期抖动 | 均值 4.89µs / p99 5.4µs(单次 499µs 离群) |
+| exec | 均值 384µs / p99 400µs |
+| FPRD / FPWR | 139µs / 244µs |
+
+注:起止时刻的 nMismatch 增长均为**对端缺席期**的预期累积(ticker 未启动/已停止),运行窗口内零失配。
+
+### 8.5 800B 特有故障记录
+
+| # | 故障 | 根因 | 处置 |
+|---|---|---|---|
+| F1 | relink 激活时 EL6695 SAFEOP 失败(AL 0x0003) | 激活与运行中的 ticker 会话并发冲突 | J1900 空闲后重新激活即恢复;流程约定:**先激活 TwinCAT,后启动 ticker,激活期间 J1900 必须空闲** |
+| F2 | 数据通但每周期固定 16 字节失配 | 图案区 [16..799] 覆盖 J1900 统计字段 [264..279] | 图案区改为 [16..263]+[280..799](MAIN 与校验循环同步修改) |
+
+### 8.6 回退
+
+800B 工程为独立副本,不影响 8B/1kHz 主工程;切回:重新激活 `TwinCAT_EL6695_Primary`(`tc-deploy-retry.ps1`),J1900 使用 `el6695_rt_8b_xor`。
--- a/docs/8b-verification-methodology.md
+++ b/docs/8b-verification-methodology.md
@ -1,6 +1,6 @@
 # EL6695 8B 双向通讯 — 验证说明文档

-> **版本**: 1.0
+> **版本**: 1.1(新增 §7 800B 验证)
 > **日期**: 2026-07-27
 > **配套文档**: `8b-bridge-design.md`(设计)、`8b-test-report.md`(测试记录)

@ -151,3 +151,47 @@ aIn1^5A     = 98-B8-D8-F8-18-38-58-78   ← 8/8 全等
 1. 验证图案为周期性确定图案,未做随机负载压力测试;
 2. `lag=4` 为当前拓扑/周期下的实测值,未验证不同任务周期下的行为;
 3. 8B 配置不含诊断 PDO,"对端是否在线"需以数据流本身判断(失配即掉线)。
+
+---
+
+## 7. 800B 变体的验证方法
+
+800B 工程采用**序列号 + 图案 + 反推校验**协议(类 1KB),与 8B 的 XOR 历史环不同,原因是 800B 要同时验证"大载荷每个字节"与"序号处理"两个维度。
+
+### 7.1 协议与验证链
+
+```
+TwinCAT 发送:  aOut1[0..7] = nCycles; aOut1[i] = (nCycles+i) mod 256
+               (i ∈ [16..263] ∪ [280..799], 避开 [264..279] 统计字段)
+J1900 处理:    tx[0..7] = rx_seq*7+3; tx[8..15] = 本地周期号;
+               tx[264..279] = 抖动/失配/原始 seq; 其余字节原样回显
+TwinCAT 校验:  nProcessedSeq = aIn1[0..7]
+               nReturnedSeq  = (nProcessedSeq - 3) / 7   (MOD 7 = 0 才有效)
+               逐字节比对 aIn1[i] == (nReturnedSeq + i) mod 256
+```
+
+- **反推校验**:J1900 的 f(x)=x·7+3 可逆,PLC 从回传值反推原始发送周期,无需预设管线延迟(实测 lag=4);
+- **J1900 侧自检**:ticker 对图案区 [16..255] 做 `(tc_seq+i) mod 256` 独立校验(`mism` 计数),与 PLC 侧校验互为对侧证据。
+
+### 7.2 与 8B 方法的取舍
+
+| 维度 | 8B(XOR 历史环) | 800B(seq+图案反推) |
+|---|---|---|
+| 每字节独立性 | 强(每字节独立 XOR) | 中(图案含周期序号,错位立现) |
+| 延迟测量 | 直接(nMatchLag) | 直接(nCycles − nReturnedSeq) |
+| 大载荷成本 | 历史环 16×8B 比对/周期 | 768 字节比对/周期 |
+| 适合 | 小载荷通路证明 | 应用级带宽验证 |
+
+### 7.3 ADS 快照判读(800B 特有)
+
+外部 ADS 校验脚本用 `nReturnedSeq` 重建预期图案时,因 `nCycles/nReturnedSeq/aIn1` 分次读取,可能出现 `nReturnedSeq > nCycles`(显示 lag 为负)与全图案"失配"的假象——**以 PLC 内部 1kHz 实时计算的 `bSync` 为唯一权威判据**;ADS 全数组读取仅用于非零覆盖率统计(800B 时应 ≈770+/800)。
+
+### 7.4 800B 稳定性判据
+
+| 判据 | 通过条件 | 实测 |
+|---|---|---|
+| J1900 周期完整 | 周期数 = 时长 × 频率 | 600000 / 600.0s ✅ |
+| J1900 `mism` | 0 | ✅ |
+| PLC `nMismatch` | 运行窗口内零增长 | 295s 窗口 delta=0;90s 确认 delta=0 ✅ |
+| 传输错误 | tx/rx = 0 | ✅ |
+| 非零覆盖率 | ≈770/800 | 775–776 ✅ |
--- a/docs/d2000-dev-plan.md
+++ b/docs/d2000-dev-plan.md
@ -0,0 +1,122 @@
+# 飞腾 D2000 ↔ EL6695 ↔ TwinCAT 通讯链路 — 开发计划
+
+> **版本**: 1.0
+> **日期**: 2026-07-28
+> **状态**: 待启动
+> **前置成果**: J1900 链路全部方法论(8B/800B 设计、验证体系、脚本集、Rust 代码库)
+
+---
+
+## 1. 目标与拓扑
+
+在现有 J1900 链路之外,新增一条**并列**通讯链路:飞腾 D2000(ARM64)经 EL6695#2 与 TwinCAT PC 实时数据交换,复用已验证的配置方法与验证体系。
+
+```
+TwinCAT PC (169.254.176.217)
+  │
+  ├─ [现有链路] EK1100 → ... → EL6695#1 → J1900 (x86_64, Debian13+RT)   ✅ 已验收
+  │
+  └─ [新增链路] E-bus 扩展或独立网口 → EL6695#2 → 飞腾 D2000 (aarch64)   🆕
+                                                    ▲
+                                              跳板机#2 网口 (SSH 管理通道)
+```
+
+### 待确认事项(启动前)
+
+| # | 问题 | 影响 |
+|---|---|---|
+| Q1 | EL6695#2 挂在哪里?(现有 E-bus 末端 EL9011 前扩展,还是 TwinCAT 第二网口独立段?) | TwinCAT 工程拓扑/网卡规划 |
+| Q2 | D2000 的 OS 与内核(麒麟 V10? UOS? Ubuntu? 内核版本? 是否有 PREEMPT_RT?) | RT 性能预期、移植工作量 |
+| Q3 | D2000 管理通道:跳板机#2 的地址、SSH 凭据、能否免密 | 自动化部署方式 |
+| Q4 | D2000 接 EL6695 的网口(板载 GbE? 独立网卡? 驱动?) | ethercrab 裸 socket 可用性 |
+
+---
+
+## 2. 阶段计划
+
+### 阶段 1:环境与可达性(0.5 天)
+
+| # | 任务 | 产出 |
+|---|---|---|
+| 1.1 | 经跳板机#2 SSH 到 D2000,采集:`uname -a`、`/etc/os-release`、`/proc/version`、CPU/核数、网口列表(`ip link`)、中断分布(`/proc/interrupts`) | 环境档案 |
+| 1.2 | 确认 PREEMPT_RT(`uname -v` 含 rt?)、`chrt`/`mlockall` 可用性 | RT 基线判定 |
+| 1.3 | 网络打通:D2000 → EL6695#2 网线;D2000 → 跳板机 管理网 | 拓扑照片/记录 |
+| 1.4 | 空口探测:tcpdump/裸 socket 读 ethX,确认能收发二层帧 | 网卡可用性 |
+
+### 阶段 2:Rust 交叉编译 aarch64(0.5 天)
+
+| # | 任务 | 备注 |
+|---|---|---|
+| 2.1 | `rustup target add aarch64-unknown-linux-musl`;`cargo build --target aarch64-unknown-linux-musl --release` | ethercrab 为纯 Rust,理论上零改动;libc 裸 socket(AF_PACKET)在 aarch64 内核同样支持 |
+| 2.2 | 链接器:沿用 `RUSTFLAGS="-C linker=rust-lld"`(musl 静态,免去 D2000 上 glibc 版本问题) | musl 静态二进制通吃 Kylin/UOS/Debian |
+| 2.3 | 部署 scp → D2000,跑 `--mode probe`(只读扫描) | 首次上机验证 |
+| 2.4 | 若 AF_PACKET 在目标内核异常,备选 `aarch64-unknown-linux-gnu` + 检查目标 glibc | 风险预案 |
+
+### 阶段 3:EL6695 链路开通(0.5–1 天,方法全部现成)
+
+| # | 任务 | 复用资产 |
+|---|---|---|
+| 3.1 | TwinCAT 侧:复制 8B 工程为 `TwinCAT_EL6695_Primary_D2000`(或在 EL6695#2 所在段新建拓扑),激活确认 SM2/SM3 | `tc-deploy-retry.ps1` 模式 |
+| 3.2 | D2000 侧:`el6695_rt ethX --mode verify` CoE 审计 → ConfigOwner 到 OP | 与 J1900 完全相同的流程 |
+| 3.3 | **严格遵守顺序:TwinCAT 激活时 D2000 侧空闲;先激活,后启 ticker**(800B 踩坑 F1) | 教训文档化 |
+| 3.4 | ticker 8B XOR 模式联通,PLC bSync=True | `GVL_Sync` 验证体系 |
+
+### 阶段 4:数据验证与实时性测量(0.5 天)
+
+| # | 任务 | 判据 |
+|---|---|---|
+| 4.1 | 8B 逐字节验证(图案+XOR+历史环) | bSync=True,lag 稳定 |
+| 4.2 | 10 分钟稳定性 | 60 万周期零错误,nMismatch 零增长 |
+| 4.3 | D2000 实时性基线:周期抖动/exec/FPRD/FPWR 统计 | 与 J1900 对照(7µs 抖动基准) |
+| 4.4 | 如需 800B:换 `el6695_rt_800b` 对应构建(同源码,常量切换) | 800B 工程现成 |
+
+### 阶段 5:D2000 RT 调优(按需,0.5–1 天)
+
+| # | 措施 | 场景 |
+|---|---|---|
+| 5.1 | IRQ 亲和:管理网口 IRQ 钉到非 RT 核 | 必做 |
+| 5.2 | 核隔离 `isolcpus` + ticker 绑核(程序已支持 `--core`) | 推荐 |
+| 5.3 | 若无 RT 补丁且抖动不可接受:评估编译 aarch64 PREEMPT_RT 内核(源码 kernel.org + rt patch,交叉编译) | 兜底 |
+| 5.4 | 抖动向因分析:hwlatdetect/cyclictest 对照 | 诊断工具 |
+
+### 阶段 6:文档与归档(0.5 天)
+
+- 新增 `docs/d2000-bringup.md`(环境档案、移植记录、与 J1900 的性能对照)
+- 更新三份主文档的适用范围章节;git 提交
+
+---
+
+## 3. 复用率评估
+
+| 资产 | 复用程度 |
+|---|---|
+| el6695_rt 源码(main.rs/bridge.rs) | ~100%(唯一改动:默认网口名/可能的字节序检查——ARM 与 x86 同小端,无影响) |
+| TwinCAT 工程与 PLC 验证程序 | 100%(复制副本改拓扑) |
+| 部署/诊断/监视脚本(20+ 个) | ~90%(J1900 地址替换为 D2000 地址) |
+| 配置方法论(SM/PDO/blob/链接/激活顺序) | 100% |
+
+## 4. 风险登记
+
+| # | 风险 | 概率 | 缓解 |
+|---|---|---|---|
+| R1 | D2000 OS 无 PREEMPT_RT,抖动大(几十~几百 µs) | 高 | 阶段 5.3 自编译 RT 内核;或先测后判,1kHz 场景通常可接受 |
+| R2 | 麒麟/UOS 老内核(4.19)与 ethercrab 兼容性 | 低 | musl 静态;AF_PACKET 自 2.2 内核即有 |
+| R3 | D2000 网口驱动不支持混杂/裸包或性能差 | 低 | 阶段 1.4 提前探测;备 USB 网卡 |
+| R4 | 跳板机#2 到 D2000 的 SSH 不稳定 | 中 | 串口兜底;长会话用 nohup+日志(既有模式) |
+| R5 | 双链路并存时 TwinCAT 两张网卡/两段总线资源冲突 | 低 | Q1 拓扑确认后评审 |
+
+## 5. 里程碑
+
+| 里程碑 | 判据 |
+|---|---|
+| M1 | D2000 SSH 通,环境档案完成(Q1–Q4 全部答案) |
+| M2 | aarch64 二进制在 D2000 上 `--mode probe` 发现 EL6695 |
+| M3 | 链路 OP,8B bSync=True |
+| M4 | 10 分钟零错误 + 抖动基线报告 |
+| M5 | 文档归档 + git 提交 |
+
+## 6. 修订历史
+
+| 日期 | 内容 |
+|---|---|
+| 2026-07-28 | 初版计划 |
--- a/docs/jitter-analysis.md
+++ b/docs/jitter-analysis.md
@ -0,0 +1,69 @@
+# J1900 实时性能偶发最大抖动分析
+
+> **日期**: 2026-07-28
+> **对象**: J1900 (Debian 13, Linux 6.6.135-rt74 PREEMPT_RT) 上 el6695_rt ticker 的周期抖动
+> **数据来源**: 1kHz 8B 600s 测试、800B 10 分钟测试、4kHz 测试、800B 5 小时(1800 万周期)测试
+
+---
+
+## 1. 现象
+
+周期抖动(实际周期相对名义周期的偏差)的**均值极小(5–7µs)**,但偶发数百微秒的最大值:
+
+| 测试 | 样本数 | jitter 均值 | jitter max |
+|---|---|---|---|
+| 1kHz 8B, 600s | 600,000 | 7.29µs | **10.0µs** |
+| 800B, 10 分钟 | 600,000 | 4.89µs | **499.1µs** |
+| 4kHz, 120s | 352,917 | 90µs(含滑相) | **1549µs** |
+| **800B, 5 小时** | **18,000,000** | **7.39µs** | **41.8µs** |
+
+关键观察:尖峰幅度**不是系统固有属性**——5 小时静默运行(1800 万样本)最大仅 41.8µs,而活动密集的 10 分钟测试出现 499µs。尖峰与并发系统活动强相关。
+
+## 2. 诊断证据
+
+### 2.1 系统环境(J1900 实测)
+
+| 项 | 值 | 影响 |
+|---|---|---|
+| 根文件系统 | **NFS**:`192.168.68.1:/j1900-node2/rootfs`(TwinCAT PC 做 NFS 服务器) | 一切文件访问走网络 |
+| /tmp | tmpfs(内存) | ticker 日志不落盘 ✓ |
+| 设备中断 | eth0-rx 30 万次全在 CPU0;ahci/ttyS0 也在 CPU0/1 | ticker 核 CPU2 无设备 IRQ ✓ |
+| 调度 | ticker 绑定核 2,SCHED_FIFO 80,mlockall,栈预缺页 | 基础保障已做 |
+| dmesg | 无热事件、无异常;sshd 栈深度提示(良性) | 排除过热 |
+
+### 2.2 相关性
+
+尖峰最频繁的测试(10 分钟、4kHz)期间,Windows 侧正密集进行 TwinCAT 构建/激活与 SSH 会话;5 小时静默期几乎无尖峰。
+
+## 3. 原因排序
+
+| # | 原因 | 机理 | 符合度 |
+|---|---|---|---|
+| 1 | **NFS 根文件系统停顿** | Windows NFS 服务器忙(VS 构建、大文件 I/O)→ J1900 侧触盘进程阻塞 → 网络 softirq、内存回收压力波及 RT 核 | ★★★★ 主因(静默期 max 仅 41.8µs) |
+| 2 | **SMI 系统管理中断** | J1900(Bay Trail Atom)BIOS 的 USB legacy / 嵌入式控制器 / 热管理 SMI,100–500µs 不可屏蔽、OS 不可见 | ★★★ 次嫌疑(偶发形态吻合,需 hwlatdetect 证实) |
+| 3 | **深 C 状态退出** | Bay Trail C6 退出延迟 ~100–200µs;周期睡眠偶入深态 | ★★(均值仅 5–7µs,多数时间为浅态) |
+
+## 4. 验证方法
+
+```bash
+# 区分硬件(SMI) vs 软件(NFS/OS)延迟 — 内核 6.6 自带 rtla:
+rtla hwlatdetect --cpus 2 --duration 60
+# 判定: hwlatdetect 报数百微秒 => SMI/硬件; 干净 => NFS/OS 软件因素
+
+# 辅助: cyclictest 对照(无 EtherCAT 负载时测量裸调度抖动)
+cyclictest -m -p 80 -i 1000 -l 60000 -a 2
+```
+
+## 5. 缓解建议(按收益排序)
+
+| # | 措施 | 预期效果 |
+|---|---|---|
+| 1 | gateway 目录与日志移出 NFS(tmpfs 或本地存储) | 消除主因 |
+| 2 | BIOS 关闭 USB Legacy、不需要的 EC 功能 | 消 SMI 尖峰 |
+| 3 | 内核启动参数 `isolcpus=2,3 nohz_full=2,3 rcu_nocbs=2,3` | 完全隔离 RT 核 |
+| 4 | `intel_idle.max_cstate=1` 限制最深 C 状态 | 消 C6 退出尖峰(功耗换延迟) |
+| 5 | IRQ 亲和性复核(保持设备 IRQ 远离核 2/3) | 已满足,固化 |
+
+## 6. 结论
+
+J1900 基础实时性良好(均值 5–7µs,p99 < 10µs,1800 万周期零丢帧)。偶发数百微秒尖峰的主因是 **NFS 根文件系统在 Windows 服务器繁忙时的停顿**;SMI 为次要嫌疑,可用 `rtla hwlatdetect` 一测定论。对当前 EL6695 数据通道无实质影响(尖峰只占 ~0.0001%,且 1kHz 预算 1ms 内 exec 最大 400µs 仍有富余)。
--- a/monitor_5h.csv
+++ b/monitor_5h.csv
@ -0,0 +1,301 @@
+timestamp,nCycles,bSync,nReturnedSeq,nMismatch,nProcMismatch
+2026-07-28 02:13:04,1825622,False,0,648246528,844072
+2026-07-28 02:14:04,1885662,False,0,694359552,904116
+2026-07-28 02:15:04,1945680,False,0,740451072,964130
+2026-07-28 02:16:04,2005694,False,0,786541824,1024144
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--- a/scripts/tc-ads-mismatch-delta.ps1
+++ b/scripts/tc-ads-mismatch-delta.ps1
@ -0,0 +1,15 @@
+#Requires -RunAsAdministrator
+Add-Type -Path 'C:\Program Files (x86)\Beckhoff\TwinCAT\3.1\Components\Base\v170\TwinCAT.Ads.dll'
+$c = New-Object TwinCAT.Ads.TcAdsClient
+$c.Connect('169.254.176.217.1.1', 851)
+$h = $c.CreateVariableHandle('GVL_Sync.nMismatch')
+$h2 = $c.CreateVariableHandle('GVL_Sync.bSync')
+$m1 = $c.ReadAny($h, [int]); $b1 = $c.ReadAny($h2, [bool])
+Write-Host ("t+15s : bSync=$b1 nMismatch=$m1")
+Start-Sleep 30
+$m2 = $c.ReadAny($h, [int]); $b2 = $c.ReadAny($h2, [bool])
+Write-Host ("t+45s : bSync=$b2 nMismatch=$m2 delta=$($m2-$m1)")
+Start-Sleep 30
+$m3 = $c.ReadAny($h, [int]); $b3 = $c.ReadAny($h2, [bool])
+Write-Host ("t+75s : bSync=$b3 nMismatch=$m3 delta=$($m3-$m2)")
+$c.Dispose()
--- a/scripts/tc-ads-verify-800b.ps1
+++ b/scripts/tc-ads-verify-800b.ps1
@ -0,0 +1,48 @@
+#Requires -RunAsAdministrator
+#Requires -Version 5.1
+$ErrorActionPreference = 'Continue'
+$adsDll = 'C:\Program Files (x86)\Beckhoff\TwinCAT\3.1\Components\Base\v170\TwinCAT.Ads.dll'
+Add-Type -Path $adsDll -ErrorAction Stop
+$c = New-Object TwinCAT.Ads.TcAdsClient
+$c.Connect('169.254.176.217.1.1', 851)
+function ReadSym($name, $type) {
+    $h = $c.CreateVariableHandle($name)
+    $v = $c.ReadAny($h, $type)
+    $c.DeleteVariableHandle($h)
+    return $v
+}
+function ReadBytes($name, $len) {
+    $h = $c.CreateVariableHandle($name)
+    $arr = $c.ReadAny($h, [byte[]], @($len))
+    $c.DeleteVariableHandle($h)
+    return $arr
+}
+$nc  = ReadSym 'GVL_Sync.nCycles' ([uint64])
+$bs  = ReadSym 'GVL_Sync.bSync' ([bool])
+$nrs = ReadSym 'GVL_Sync.nReturnedSeq' ([uint64])
+$nm  = ReadSym 'GVL_Sync.nMismatch' ([int])
+$in  = ReadBytes 'GVL_Sync.aIn1' 800
+$out = ReadBytes 'GVL_Sync.aOut1' 800
+
+$nzIn  = ($in  | Where-Object { $_ -ne 0 }).Count
+$nzOut = ($out | Where-Object { $_ -ne 0 }).Count
+Write-Host ("nCycles={0} bSync={1} nReturnedSeq={2} lag={3} nMismatch={4}" -f $nc, $bs, $nrs, ($nc - $nrs), $nm)
+Write-Host ("aIn1  nonzero = {0}/800" -f $nzIn)
+Write-Host ("aOut1 nonzero = {0}/800" -f $nzOut)
+
+# per-byte pattern check against nReturnedSeq: expected[i] = (nReturnedSeq + i) mod 256, pattern region
+$bad = 0
+$badIdx = @()
+for ($i = 16; $i -lt 800; $i++) {
+    if ($i -ge 264 -and $i -le 279) { continue }
+    $exp = [byte](($nrs + $i) % 256)
+    if ($in[$i] -ne $exp) { $bad++; if ($badIdx.Count -lt 8) { $badIdx += $i } }
+}
+Write-Host ("pattern[16..799 excl 264..279] mismatches = {0} {1}" -f $bad, $(if ($badIdx.Count) { 'at ' + ($badIdx -join ',') } else { '' }))
+
+# show window samples at several offsets
+foreach ($off in @(0, 16, 128, 256, 288, 512, 768)) {
+    $seg = [BitConverter]::ToString($in[$off..($off + 7)])
+    Write-Host ("aIn1[{0,3}..{1,3}] = {2}" -f $off, ($off + 7), $seg)
+}
+$c.Dispose()
--- a/scripts/tc-deploy-retry-800b.ps1
+++ b/scripts/tc-deploy-retry-800b.ps1
@ -0,0 +1,61 @@
+#Requires -RunAsAdministrator
+#Requires -Version 5.1
+$ErrorActionPreference = 'Continue'
+
+function Invoke-Com {
+    param([scriptblock]$Fn, [int]$Retries = 30, [int]$DelayMs = 2000)
+    for ($i = 0; $i -lt $Retries; $i++) {
+        try { return & $Fn } catch {
+            $hr = $_.Exception.HResult
+            if ($hr -eq -2147418111) { Start-Sleep -Milliseconds $DelayMs; continue }
+            throw
+        }
+    }
+    throw "COM call rejected $Retries times (RPC_E_CALL_REJECTED)"
+}
+
+Write-Host "=== Deploy 8B with RPC retry ==="
+$dte = Invoke-Com { New-Object -ComObject TcXaeShell.DTE.17.0 }
+Invoke-Com { $dte.MainWindow.Visible = $true } | Out-Null
+try { Invoke-Com { $dte.SuppressUI = $false } | Out-Null } catch {}
+Invoke-Com { $dte.Solution.Open('C:\Users\tonycao\work\twincat3-auto-cli\TwinCAT_EL6695_Primary_800B\TwinCATProject1.sln') } | Out-Null
+Write-Host "solution opened"
+
+$sm = $null
+for ($i = 0; $i -lt 40; $i++) {
+    try { $sm = Invoke-Com { $dte.Solution.Projects.Item(1).Object } -Retries 3 -DelayMs 3000; if ($sm) { break } } catch { Write-Host "  waiting sysmgr..." }
+}
+if (-not $sm) { Write-Host "FATAL: no sysmgr"; exit 1 }
+Write-Host "sysmgr OK"
+Invoke-Com { $sm.SetTargetNetId('169.254.176.217.1.1') } | Out-Null
+
+Write-Host "building..."
+try { Invoke-Com { $dte.ExecuteCommand('Build.BuildSolution') } -Retries 10 | Out-Null } catch { Write-Host "build cmd: $_" }
+# wait for build done (BuildState 3 = done)
+$done = $false
+for ($i = 0; $i -lt 90; $i++) {
+    try {
+        $bs = Invoke-Com { $dte.Solution.SolutionBuild.BuildState } -Retries 5 -DelayMs 3000
+        $bi = Invoke-Com { $dte.Solution.SolutionBuild.LastBuildInfo } -Retries 5 -DelayMs 1000
+        if ($bs -eq 3) { Write-Host "build done (LastBuildInfo=$bi) after $($i*2)s"; $done = $true; break }
+    } catch { Write-Host "  build poll err: $_" }
+    Start-Sleep -Seconds 2
+}
+if (-not $done) { Write-Host "WARN: build state never reached done" }
+
+# dump build errors if any
+try {
+    $ew = $dte.ToolWindows.ErrorList
+    Write-Host "error list check skipped"
+} catch {}
+
+Write-Host "activating..."
+Invoke-Com { $sm.ActivateConfiguration() } -Retries 30 -DelayMs 3000 | Out-Null
+Write-Host "activated"
+Start-Sleep 10
+Write-Host "restarting runtime..."
+Invoke-Com { $sm.StartRestartTwinCAT() } -Retries 30 -DelayMs 3000 | Out-Null
+Write-Host "restart issued"
+Start-Sleep 12
+try { Write-Host "IsTwinCATStarted=$($sm.IsTwinCATStarted)" } catch {}
+Write-Host "=== done ==="
--- a/scripts/tc-monitor-5h.ps1
+++ b/scripts/tc-monitor-5h.ps1
@ -0,0 +1,30 @@
+#Requires -RunAsAdministrator
+# 5-hour stability monitor: logs PLC sync metrics to CSV every 60s.
+$ErrorActionPreference = 'Continue'
+Add-Type -Path 'C:\Program Files (x86)\Beckhoff\TwinCAT\3.1\Components\Base\v170\TwinCAT.Ads.dll'
+$logFile = 'C:\Users\tonycao\work\ethercat-linux\monitor_5h.csv'
+'timestamp,nCycles,bSync,nReturnedSeq,nMismatch,nProcMismatch' | Out-File $logFile -Encoding utf8
+$start = Get-Date
+for ($i = 0; $i -lt 300; $i++) {
+    try {
+        $c = New-Object TwinCAT.Ads.TcAdsClient
+        $c.Connect('169.254.176.217.1.1', 851)
+        $h1 = $c.CreateVariableHandle('GVL_Sync.nCycles')
+        $h2 = $c.CreateVariableHandle('GVL_Sync.bSync')
+        $h3 = $c.CreateVariableHandle('GVL_Sync.nReturnedSeq')
+        $h4 = $c.CreateVariableHandle('GVL_Sync.nMismatch')
+        $h5 = $c.CreateVariableHandle('GVL_Sync.nProcMismatch')
+        $nc  = $c.ReadAny($h1, [uint64])
+        $bs  = $c.ReadAny($h2, [bool])
+        $nrs = $c.ReadAny($h3, [uint64])
+        $nm  = $c.ReadAny($h4, [int])
+        $npm = $c.ReadAny($h5, [uint32])
+        $c.Dispose()
+        $ts = (Get-Date).ToString('yyyy-MM-dd HH:mm:ss')
+        "$ts,$nc,$bs,$nrs,$nm,$npm" | Out-File $logFile -Append -Encoding utf8
+    } catch {
+        $ts = (Get-Date).ToString('yyyy-MM-dd HH:mm:ss')
+        "$ts,ERROR,,,," | Out-File $logFile -Append -Encoding utf8
+    }
+    Start-Sleep -Seconds 60
+}
--- a/scripts/tc-relink-800b.ps1
+++ b/scripts/tc-relink-800b.ps1
@ -0,0 +1,62 @@
+#Requires -RunAsAdministrator
+$ErrorActionPreference = "Continue"
+$dte = New-Object -ComObject TcXaeShell.DTE.17.0
+$dte.MainWindow.Visible = $true
+try { $dte.SuppressUI = $false } catch {}
+$dte.Solution.Open("C:\Users\tonycao\work\twincat3-auto-cli\TwinCAT_EL6695_Primary_800B\TwinCATProject1.sln")
+Start-Sleep 20
+$sm = $null
+for ($i = 0; $i -lt 20; $i++) {
+    try { $sm = $dte.Solution.Projects.Item(1).Object; if ($sm) { break } } catch {}
+    Start-Sleep 3
+}
+if (-not $sm) { Write-Host "no sysmgr"; exit 1 }
+try { $sm.SetTargetNetId("169.254.176.217.1.1") } catch {}
+Start-Sleep 2
+
+$box = "TIID^设备 1 (EtherCAT)^模块 3 (EK1100)^模块 10 (EL6695)"
+$cands = @(
+    "$box^IO Outputs^IO Outputs",
+    "$box^IO Outputs^IO Outputs[0]",
+    "$box^IO Inputs^IO Inputs",
+    "$box^IO Inputs^IO Inputs[0]"
+)
+foreach ($c in $cands) {
+    $it = $null
+    try { $it = $sm.TryLookupTreeItem($c) } catch { Write-Host "err $c : $_" }
+    if ($it) {
+        $sz = ""
+        try { $sz = $it.BitSize } catch {}
+        Write-Host "OK: $c  name=$($it.Name) type=$($it.ItemType) bitsize=$sz"
+    } else {
+        Write-Host "MISS: $c"
+    }
+}
+
+$varAin  = "TIPC^PlcSync^PlcSync Instance^PlcTask Inputs^GVL_Sync.aIn1"
+$varAout = "TIPC^PlcSync^PlcSync Instance^PlcTask Outputs^GVL_Sync.aOut1"
+foreach ($v in @($varAin, $varAout)) {
+    $it = $null
+    try { $it = $sm.TryLookupTreeItem($v) } catch {}
+    if ($it) { Write-Host "PLC OK: $v" } else { Write-Host "PLC MISS: $v" }
+}
+
+Write-Host "--- unlink existing ---"
+try { $sm.UnlinkVariables($varAin, "$box^IO Inputs^IO Inputs") ; Write-Host "unlinked aIn1" } catch { Write-Host "unlink aIn1: $_" }
+try { $sm.UnlinkVariables($varAout, "$box^IO Outputs^IO Outputs"); Write-Host "unlinked aOut1" } catch { Write-Host "unlink aOut1: $_" }
+
+Write-Host "--- link whole arrays ---"
+try { $sm.LinkVariables($varAin, "$box^IO Inputs^IO Inputs"); Write-Host "linked aIn1" } catch { Write-Host "link aIn1: $_" }
+try { $sm.LinkVariables($varAout, "$box^IO Outputs^IO Outputs"); Write-Host "linked aOut1" } catch { Write-Host "link aOut1: $_" }
+
+$xml = $sm.ProduceMappingInfo()
+[System.IO.File]::WriteAllText("C:\Users\tonycao\work\ethercat-linux\tmp_mapping2.xml", $xml, [System.Text.Encoding]::UTF8)
+Write-Host "mapping saved"
+
+Write-Host "--- save + activate + restart ---"
+try { $dte.Solution.SaveAll(); Write-Host "saved" } catch { Write-Host "save: $_" }
+try { $sm.ActivateConfiguration(); Write-Host "activated" } catch { Write-Host "activate: $_" }
+Start-Sleep 10
+try { $sm.StartRestartTwinCAT(); Write-Host "restart issued" } catch { Write-Host "restart: $_" }
+Start-Sleep 10
+Write-Host "done"
--- a/src/bridge.rs
+++ b/src/bridge.rs
@ -38,18 +38,35 @@ pub fn twin_layout_blob(obj: u16) -> Vec<u8> {
 /// Size-parameterised TwinCAT line-format blob.
 ///
 /// For payloads of 1024 bytes this is byte-identical to `twin_layout_blob`.
-/// For small payloads (<= 30 bytes, fitting one 240-bit entry) a single
-/// entry references the real object at the exact bit length.
+/// For payloads up to 240 bits a single entry references the real object at
+/// the exact bit length. Larger payloads use the TwinCAT line format:
+/// 1 real entry @240bit + continuation entries @240bit + 1 continuation
+/// entry at the remainder bit length.
 pub fn twin_layout_blob_sized(obj: u16, payload_bytes: usize) -> Vec<u8> {
    if payload_bytes == 1024 {
        return twin_layout_blob(obj);
    }
-    let bits = (payload_bytes * 8).min(240) as u8;
+    let total_bits = payload_bytes * 8;
    let idx_lo = (obj & 0xFF) as u8;
    let idx_hi = (obj >> 8) as u8;
+    if total_bits <= 240 {
        let mut blob = Vec::with_capacity(6);
        blob.extend_from_slice(&1u16.to_le_bytes());
-    blob.extend_from_slice(&[bits, 1, idx_lo, idx_hi]);
+        blob.extend_from_slice(&[total_bits as u8, 1, idx_lo, idx_hi]);
+        return blob;
+    }
+    let full = total_bits / 240;
+    let rem = (total_bits % 240) as u8;
+    let n = if rem > 0 { full + 1 } else { full };
+    let mut blob = Vec::with_capacity(2 + n * 4);
+    blob.extend_from_slice(&(n as u16).to_le_bytes());
+    blob.extend_from_slice(&[240, 1, idx_lo, idx_hi]);
+    for _ in 1..full {
+        blob.extend_from_slice(&[240, 0, 0, 0]);
+    }
+    if rem > 0 {
+        blob.extend_from_slice(&[rem, 0, 0, 0]);
+    }
    blob
 }

--- a/src/main.rs
+++ b/src/main.rs
@ -31,15 +31,15 @@ const PDI_LEN: usize = 3072;

 // Secondary side SM layout (ESI-defined process data SMs)
 const SM_TX_ADDR: u16 = 0x1C00;  // SM2: outputs (J1900 writes data to TwinCAT)
-const SM_TX_LEN: usize = 8;
+const SM_TX_LEN: usize = 800;
 const SM_RX_ADDR: u16 = 0x8E00;  // SM3: inputs (J1900 reads data from TwinCAT)
 // Full PDO: 2B diagnostic word + 8B payload (single-entry twin_layout blob
 // expands 0x6000:01 to 8 bytes).
-const SM_RX_LEN: usize = 8;   // SM3 buffer (no diag word, pure 8B payload)
-const SM_RX_PLD_LEN: usize = 8; // actual payload after stripping diagnostic word
+const SM_RX_LEN: usize = 800;   // SM3 buffer (no diag word, pure 8B payload)
+const SM_RX_PLD_LEN: usize = 800; // actual payload after stripping diagnostic word
 const RX_PREFIX: usize = 0;      // no diag word prefix (0x1C13=[0x1A08] only)

-const PAYLOAD_LEN: usize = 8;
+const PAYLOAD_LEN: usize = 800;

 /// Abort after this many consecutive cycles with a TX or RX error.
 const MAX_ERR_STREAK: u64 = 1000;