628 lines
30 KiB
Markdown
628 lines
30 KiB
Markdown
# AUTOSAR 自由运行定时器需求规范 (SRS FreeRunningTimer)
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> **文档元信息**
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| 项目 | 内容 |
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|------|------|
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| 文档标题 | Requirements on Free Running Timer（自由运行定时器需求） |
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| 文档所有者 | AUTOSAR |
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| 文档责任方 | AUTOSAR |
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| 文档标识号 | 211 |
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| 文档状态 | Final（最终版） |
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| AUTOSAR 标准分类 | Classic Platform（经典平台） |
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| 标准发布版本 | 4.4.0 |
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| 原文文档号 | AUTOSAR_SRS_FreeRunningTimer |
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---
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## 文档变更历史
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| 日期 | 发布版本 | 变更人 | 变更说明 |
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|------|---------|--------|----------|
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| 2018-10-31 | 4.4.0 | AUTOSAR Release Management | 编辑性修改 |
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| 2016-12-08 | 4.3.1 | AUTOSAR Release Management | 编辑性修改 |
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| 2016-11-30 | 4.3.0 | AUTOSAR Release Management | 编辑性修改 |
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| 2014-10-31 | 4.2.1 | AUTOSAR Release Management | 编辑性修改 |
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| 2013-10-31 | 4.1.2 | AUTOSAR Release Management | 编辑性修改 |
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| 2013-03-15 | 4.1.1 | AUTOSAR Administration | - 将需求与 BSW Feature Document 链接<br>- 根据 TPS_StandardizationTemplate 更新需求格式 |
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| 2010-09-30 | 3.1.5 | AUTOSAR Administration | 法律免责声明修订 |
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| 2008-08-13 | 3.1.1 | AUTOSAR Administration | 法律免责声明修订 |
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| 2007-12-21 | 3.0.1 | AUTOSAR Administration | - 扩展文档元信息<br>- 进行小幅布局调整 |
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| 2007-01-24 | 2.1.15 | AUTOSAR Administration | - 修订 "用户建议" 章节<br>- 新增 "修订信息" |
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| 2006-05-16 | 2.0 | AUTOSAR Administration | 初始发布 |
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---
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## 目录
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1. [本文档范围](#1-本文档范围)
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2. [使用的约定](#2-使用的约定)
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3. [缩略语和缩写](#3-缩略语和缩写)
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4. [功能概述](#4-功能概述)
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5. [需求追溯](#5-需求追溯)
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6. [需求规范](#6-需求规范)
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- 6.1 功能需求
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- 6.1.1 配置
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- 6.1.2 初始化
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- 6.1.3 正常运行
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- 6.1.4 关闭操作
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- 6.1.5 故障操作
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- 6.2 非功能需求
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- 6.2.1 时间需求
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- 6.2.2 资源使用
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7. [引用的 AUTOSAR 文档](#7-引用的-autosar-文档)
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---
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## 免责声明
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> 本节保留原文，不进行翻译。
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---
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## 1. 本文档范围
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本文档定义了对软件自由运行定时器（Software Free Running Timer, SWFRT）功能的需求。OS SWS 规范应满足这些需求。
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**约束**
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特定微控制器的硬件可能无法支持自由运行定时器功能 — 那么此功能**应被省略**。尤其是以下情况：
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- 硬件定时器不可用（或被用于具有不兼容需求的其他功能）
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- 硬件定时器可用，但不独立。依赖关系不合适
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- 硬件定时器不满足范围/分辨率/间隔要求
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- 预分频器不可用或不足
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- 硬件定时器可用，但使用会导致过高的中断负载。即通过软件模拟自由运行定时器使 CPU 承担巨大计算负载意义不大
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可配置性及其对其他模块的依赖是此模块中至关重要的部分，因为通常情况下，用于自由运行定时器的定时器应在模块之间共享。实现 SW-FRT 的模块应导入其他工具关于定时器/时钟的设置，而非自行定义。
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---
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## 2. 使用的约定
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- AUTOSAR 文档中需求的表示遵循 [5] 指定的表格。
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- 在需求中，应使用以下特定语义（基于 IETF 的语义）：
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- **SHALL（应当）**：该词表示相关定义是规范的绝对要求。
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- **SHALL NOT（不得）**：该短语表示相关定义是规范的绝对禁止。
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- **MUST（必须）**：该词表示相关定义是出于法律问题的绝对要求。
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- **MUST NOT（不应）**：该短语表示相关定义是出于法律约束的绝对禁止。
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- **SHOULD（建议）**：该词或形容词 "RECOMMENDED" 表示在特定环境下可能存在忽略某一项目的有效理由。
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- **SHOULD NOT（不建议）**：该短语或短语 "NOT RECOMMENDED" 表示在特定环境下某种行为可能是可接受的或甚至有用。
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- **MAY（可以）**：该词或形容词 "OPTIONAL" 表示该项目是真正可选的。
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---
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## 3. 缩略语和缩写
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| 缩写 | 描述 |
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|------|------|
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| API | Application Programming Interface（应用程序编程接口） |
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| BSW | Basic Software（基础软件） |
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| COM | Communications（通信） |
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| ECU | Electronic Control Unit（电子控制单元） |
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| GPT | General Purpose Timer（通用目的定时器，SWS 模块） |
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| HW | Hardware（硬件） |
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| Tick | HW 定时器的一次增量 = HW Timer Tick；若未明确说明，则指硬件定时器。TickType 由许多 HW-Timer Ticks 组成；若意指此，将明确指出。 |
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| Interval of Timer | 两个测量点之间的时间距离 |
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| OS | AUTOSAR Operating System（AUTOSAR 操作系统） |
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| Range of Timer | 定时器可能覆盖的最大间隔 |
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| Reset Timer | 以预定义值在超过预定义边界时启动的定时器 |
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| Resolution of Timer | 可测量的最小时间间隔 |
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| SI | International System of Units（国际单位制，源自法语 Système International d'Unités） |
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| SLA | Software Layered Architecture（软件分层架构） |
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| SWC | Software Component（软件组件） |
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| SWFRT | Software extending features of HW Free running timers（扩展 HW 自由运行定时器功能的软件） |
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| Test Value | 与当前读数进行比较的测试值 |
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| Wrap Around | 定时器达到定义的最大值时执行的操作 |
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每个需求都有其唯一标识符，以 `SWFRT` 作为前缀。
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---
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## 4. 功能概述
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本章描述了对自由运行定时器模块功能的需求。第 4.1 节通过概述介绍 SWFRT，第 4.2 和 4.3 节包含需求。该功能将被底层 SW 以及应用程序访问。因此在 SLA 中的位置需要在服务区域（SLA ID: 02-06）。
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**范围内功能：**
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**A)** 软件自由运行定时器（SWFRT）模块提供一段访问一个或多个硬件定时器的代码。此硬件定时器在运行时不得被任何其他 SW 模块修改（自由运行的硬件定时器或复位定时器，SRS_Gpt_12404：配置为连续模式）。定时器也可能执行具有不同目的的功能。SWFRT 代码将可能变化的硬件功能始终映射到相同的 SW 功能：
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- SWFRT 在尚未经过任何时间时从零开始。
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- SWFRT 递增至最大值。最大值可能与字节/字/...最大值不同。
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- 超过最大值的增量会重新从零开始 SWFRT（这可能是 wrap around 的一种特殊情况）。
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功能 A) 抽象了 GPT 读出函数（SRS_Gpt_12117）或直接硬件访问（定时器单元可能由 OS 直接管理，见第 5 章 SWS OS）。
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**B)** SWFRT 还应扩展硬件可能的受限范围。尤其是当 HW 定时器的位数受限时，需要扩展范围。为此扩展，SWFRT 增加一个循环计数器。该计数器计数的间隔是 HW 定时器的最大范围。
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用于功能 A) 和功能 B) 的 HW 定时器不一定是同一定时器；在不同时间启动且范围不同的两个不同 HW 定时器也可以实现此功能。因此，功能 A) 的 HW 定时器与功能 B) 的定时器之间可能存在偏移。
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**范围内用例：**
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- **UC A**：SWFRT（功能 B）应能实现具有不同分辨率、不同范围和测量间隔的软件定时器。应用程序可以使用 SWFRT 测量时间（从几毫秒到数天的范围）。
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- **UC B**：已删除（编号 B：有意保留以供引用）。
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- **UC C**：SWFRT（功能 A）应能在正常程序流中启用 "小型" 的已定义时间延迟。循环可以使用 SWFRT 来监控（有故障的）硬件的时间间隔，当需要快速反应时。"小型" 应理解为无法通过 OSEK 功能满足的延迟（即几百纳秒）。
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- **UC D**：当上述延迟超过可容忍时间（例如外部硬件的响应时间非常长），在等待比 "小型" 时间间隔稍长的时间时可以应用 OS 重新调度。通过检查预期事件是否在定义的时间内发生来注册超时。
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**关于开销的限制：**
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使用两种可能功能中的哪一种取决于 SWFRT 导入的配置要求（要测量的最小和最大间隔、定时器的范围和分辨率）以及合理的资源消耗。应避免高频通知函数。即：不要使用 SRS_Gpt_12120：GPT 通知来提供长范围。而应基于调用 SWFRT 主函数的 OS 任务构建长范围。
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从用户角度的典型场景将是以下序列：
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1. 读取 HW-FRT 或计数器。
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2. 执行某些操作。
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3. 循环测试此操作的成功。
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4. 再次读出上述 FRT，且
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5. 如果与该 FRT 的后续读出之间的差异不超过预定义的超时，则将此操作标记为成功。
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SWFRT SW 功能有时使用多个递增计数器。HW 计数器的一次增量应称为 "tick"。进一步说，微控制器硬件（HW）可以提供仅递增和/或递减的定时器。ticks 将表示显著不同的值（ns、ms、s）。溢出或超过设定最大（/最小）值会自动以零（/最大）重新启动定时器。此操作称为 wrap around。在 SWFRT 定时器的定义范围内，任何时间计算都需要调整到 wrap around 值。
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应抽象硬件特性。应考虑以下特性：
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- 微控制器的外部时钟（石英晶体）
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- 微控制器的 PLL
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- 微控制器使用的时钟的（小数）预分频器
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- 使用的定时器（-组合）的微控制器寄存器宽度
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- 复位值后的 wrap around/wrap around 边界
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- 微控制器对这些寄存器的访问（！）
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- 微控制器的操作模式（Sleep/Stop/Freeze 等）
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- 微控制器定时器通道之间的时钟硬件依赖（"硬件时钟树"）
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- 缺少：
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- 系统时钟的频率调制（！），
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- 外部非基于时间的时钟供应，例如角度驱动时钟（！）
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这些硬件特性应作为配置参数（其参数集可能不可移植到不同的微控制器）与 MCU、GPT 和 OS 模块一起在本地定义。它们的集合导致一个具有定义分辨率和范围的定时器的转换规则（可能不可移植到不同配置）；生成的代码需要为每个新配置从头生成。应用这些转换规则将导致读取具有定义分辨率以及可测量的最大/最小间隔的自由运行定时器的函数（宏）。"用户"对由定时器、规则、分辨率和范围组成的一组感兴趣。
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所有以上内容将映射到相关模块的配置章节中。
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---
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## 5. 需求追溯
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| 需求 | 描述 | 满足于 |
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|------|------|--------|
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| RS_BRF_01048 | AUTOSAR 模块设计应支持模块在多任务环境中协作 | SRS_Frt_00044 |
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| RS_BRF_01056 | AUTOSAR BSW 模块应提供标准化接口 | SRS_Frt_00033, SRS_Frt_00034, SRS_Frt_00047 |
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| RS_BRF_01096 | AUTOSAR 应当支持 ECU 的启动和关闭 | SRS_Frt_00020, SRS_Frt_00029, SRS_Frt_00041, SRS_Frt_00048 |
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| RS_BRF_01104 | AUTOSAR 应当支持 ECU 和总线的睡眠与唤醒 | SRS_Frt_00048 |
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| RS_BRF_01472 | AUTOSAR 应当支持模式 | SRS_Frt_00022 |
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| RS_BRF_01856 | AUTOSAR 微控制器抽象应提供对内部 MCU 配置的访问 | SRS_Frt_00023, SRS_Frt_00024, SRS_Frt_00025, SRS_Frt_00026 |
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| RS_BRF_01904 | AUTOSAR 微控制器抽象应提供对硬件定时器的访问 | SRS_Frt_00019, SRS_Frt_00020, SRS_Frt_00021, SRS_Frt_00022, SRS_Frt_00023, SRS_Frt_00024, SRS_Frt_00025, SRS_Frt_00026, SRS_Frt_00028, SRS_Frt_00029, SRS_Frt_00030, SRS_Frt_00031, SRS_Frt_00032, SRS_Frt_00033, SRS_Frt_00034, SRS_Frt_00041, SRS_Frt_00044, SRS_Frt_00047, SRS_Frt_00048 |
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---
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## 6. 需求规范
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同一类型的需求在每个章节中按以下标题分组：
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**功能需求：**
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- 配置（模块的哪些元素需要可配置）
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- 初始化
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- 正常运行
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- 关闭操作
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- 故障操作
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- ...
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**非功能需求：**
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- 时间需求
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- 资源使用
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- 可用性
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- 向其他 WP 的输出（例如，描述模板、工具等）
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- ...
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### 6.1 功能需求
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#### 6.1.1 配置
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本节陈述对模块可配置性的需求。
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##### 6.1.1.1 [SRS_Frt_00019] 应配置硬件定时器类型
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```
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Type: New
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Description: This defines depending on range, resolution and max/min interval to
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be measured the hw-timer(s) which shall be used for which
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functionality of the SWFRT module. Pick one type of timer that
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fulfils the resolution range etc. requirements. This could be either
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a counter of OS TickType or a HW timer of the microcontroller.
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Rationale: Restrict the possibilities and the resulting variants / overhead of
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which timer type may be used for implementation
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Use Case: Define
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- allowed ranges for Quartz, PLL and if resulting timer provides a
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constant frequency,
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- whether timer shall count up or down (no hindering reason for
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use, but the necessary program will differ),
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- preferred register width,
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- if this timer requires a wrap around margin different to register
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width.
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- wrap around value,
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- whether pre-scalers may be used,
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- which values (range) for which pre-scalers may be set,
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- if / which timers could be cascaded,
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- time between wrap around,
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e.g. Pick the System Timer of Tricore
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Dependencies: --
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Supporting Material: --
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⌋(RS_BRF_01904)
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```
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##### 6.1.1.2 [SRS_Frt_00020] 如果不使用 GPT 定时器，则配置和初始化应由提供 SWFRT 功能的模块（OS）执行
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```
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Type: New
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Description: If the GPT Timer is not used the configuration and initialization shall
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be performed by the module providing the SWFRT functionality (OS).
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Rationale: Use HW most efficiently
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Use Case: There are usually timers such as "System Timer", "Periodic Interrupt
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Timer", "GPT Timer", etc. which might be used for SWFRT and other
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modules. Which type is to be used is selected by Requirement
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6.1.1.1. They have still features which need to be elaborated and
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selected per microcontroller – but not per implementation. The
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setting should not be overridden by each other nor be forgotten
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Dependencies: SRS_Frt_00021
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Supporting Material: --
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⌋(RS_BRF_01904, RS_BRF_01096)
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```
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##### 6.1.1.3 [SRS_Frt_00021] 计算 tick 持续时间所必需的元素应为导入的配置项
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```
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Type: New
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Description: The configuration of a new hw-timer is set up if appropriate hw-timer
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configuration is not available. This is a requirement on the
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dependencies in Ch 10 of the SWS. This shall ensure whether the set
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up is done by OS or whether OS will reuse a timer from a different
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module (e.g. GPT)
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Rationale: Use HW most efficiently
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Use Case: HW Timer is able to provide big range as well as resolution. It may be
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used for OS TickType as well as for timing functions of SW FRT. Just
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different mask operations need to be applied.
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Dependencies: SRS_Frt_00020
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Supporting Material: --
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⌋( RS_BRF_01904)
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```
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##### 6.1.1.4 [SRS_Frt_00022] 应能声明使用哪个硬件定时器
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```
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Type: Valid
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Description: --
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Rationale: The code will vary significant depending on the used timer
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Use Case: Define which timers will be supported.
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Dependencies: --
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Supporting Material: --
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⌋(RS_BRF_01472,RS_BRF_01904)
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```
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##### 6.1.1.5 [SRS_Frt_00023] 应设置一个 tick 的持续时间
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```
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Type: Valid
|
||
Description: Depending on the access to the timer register this results in different
|
||
resolutions – this resolution must be known.
|
||
Rationale: The combination of SRS_Frt_00021 and SRS_Frt_00020 define the
|
||
settings for which timer to be used and its rules. These rules are to
|
||
be defined per microcontroller and HW timer respectively OS
|
||
GlobalTimeTickType.
|
||
Use Case: The register TIM0 will provide one tick as 12.5 ns for a TC1766
|
||
running at a speed of 80 MHz. In use case -C- (from Introduction
|
||
chapter) a loop shall read cyclically the timer value and test a
|
||
possibly faulty hardware. The maximum test interval is 500 ns so
|
||
the difference in between first and its consecutive readings is
|
||
predefined (Pre-compile/Link/Post-build) as 40.
|
||
|
||
Either Basic SW module as well as Application is provided in this
|
||
way with an abstracted time.
|
||
Dependencies: [SRS_Frt_00021], [SRS_Frt_00020]
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01856)
|
||
```
|
||
|
||
##### 6.1.1.6 [SRS_Frt_00024] SWFRT 应支持不同的分辨率和范围
|
||
|
||
```
|
||
Type: Valid
|
||
Description: The SWFRT shall support different resolutions and ranges. I.e. set
|
||
up a set of different tick lengths in a way that ranges and
|
||
resolutions are covered. These are supported with ticks representing
|
||
different time quanta. See range definition in Table in chapter 2.1.
|
||
The range shall be assumed to start with 0 up to a maximum.
|
||
Rationale: --
|
||
Use Case: A PIT Register-set will provide one tick as 6.4 µs for a Star12
|
||
running at a speed of 40 MHz and using a pre-scaler of 256. An
|
||
access to the 16 bits of the register set register will provide ticks
|
||
in the range 0 ... 420 ms. Since intervals bigger than 420 ms cannot
|
||
be covered an additional main-function counter shall be implemented
|
||
for ranges from 0 … 2.6E3 s (1.8 days)
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01856)
|
||
```
|
||
|
||
##### 6.1.1.7 [SRS_Frt_00025] 应为不同用户提供对时间信息的访问方法
|
||
|
||
```
|
||
Type: Valid
|
||
Description: Different timers, masks to timers might be needed. If so each
|
||
access method must be defined.
|
||
Rationale: Avoid multiple conversions between tick – counting and SI unit
|
||
based comparison; use instead unique approach with predefined test
|
||
values
|
||
Use Case: There are accesses possible to a basic tick as well as an access to
|
||
every nth tick. Whereas n is dependent on the microcontroller (e.g.
|
||
reading bits 8 ... 24 of the respective counter only). If the access
|
||
crosses the bit boundary of 16/32 or exceeds one clock cycle special
|
||
care has to be put into consistency
|
||
Dependencies: SRS_Frt_00019, SRS_Frt_00020, SRS_Frt_00021, SRS_Frt_00022,
|
||
SRS_Frt_00023; SRS_Frt_00034
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01856)
|
||
```
|
||
|
||
##### 6.1.1.8 [SRS_Frt_00026] 设置目标计数值：以 SI 单位表示的时间差应在配置时离线计算
|
||
|
||
```
|
||
Type: Valid
|
||
Description: Target Count Values are those against which the read timer value
|
||
is compared. The Target Count Values shall be configured in SI
|
||
Units. The equivalent in ticks is stored in the ECU's memory.
|
||
Rationale: Runtime shall be kept low: the margins against which timer
|
||
differences are tested shall be calculated at configuration time
|
||
(instead of multiplying at runtime).
|
||
Use Case: The offline calculated target count values may be of the any
|
||
configuration class. The Target Count Values are those constants
|
||
which will be compared at runtime against the present value of the
|
||
timer. This implies that range, resolution and valid timer interval
|
||
must be respected for the compare instruction. Doing so the code
|
||
reduces to compare instructions.
|
||
|
||
Values required by user modules are expressed in their XML. The
|
||
automatic configuration editor for the SWFRT checks other modules
|
||
for times and, when it finds then, uses knowledge of the timer's
|
||
range and resolution to calculate the times in counter ticks. These
|
||
values are then placed back in the user's XML so that the user's
|
||
code generation has access to those values.
|
||
Dependencies: SRS_Frt_00025
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01856)
|
||
```
|
||
|
||
##### 6.1.1.9 [SRS_Frt_00028] 应确保连续运行模式
|
||
|
||
```
|
||
Type: Valid
|
||
Description: The used HW timer may perform functionality with different
|
||
purposes as well. This hardware shall be a free running hardware
|
||
timer or reset timer, SRS_Gpt_12404: configure as continuous mode.
|
||
Rationale: --
|
||
Use Case: --
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904)
|
||
```
|
||
|
||
#### 6.1.2 初始化
|
||
|
||
##### 6.1.2.1 [SRS_Frt_00029] 应提供与是否需要设置或修改任何寄存器无关的初始化函数
|
||
|
||
```
|
||
Type: Valid
|
||
Description: If MCU driver performs the initialization, SWFRT init function
|
||
must be called after MCU driver init had been called. If GPT driver
|
||
performs the initialization SWFRT init function must be called
|
||
after GPT driver had been called.
|
||
Rationale: Ensure timer and PLL is initialized.
|
||
Use Case: --
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01096)
|
||
```
|
||
|
||
#### 6.1.3 正常运行
|
||
|
||
##### 6.1.3.1 [SRS_Frt_00030] 读出值应从零开始
|
||
|
||
```
|
||
Type: Valid
|
||
Description: The read-out value starts with Zero; even if HW counts down from
|
||
maximum to zero
|
||
Rationale: Enable to define a standard interface
|
||
Use Case: e.g. hardware starts with 0xE000 and runs down to 0x100, due to
|
||
some scaling factors needed, all adaptations to the read out value
|
||
shall be done within SWFRT
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904)
|
||
```
|
||
|
||
##### 6.1.3.2 [SRS_Frt_00031] SWFRT 应递增，即连续读出值将增加 — 除非超出 SWFRT 的定义范围
|
||
|
||
```
|
||
Type: Valid
|
||
Description: This means: invert the counter when the HW timer counts down;
|
||
this means further on: adjust any offsets which may be present
|
||
when HW timer counts from an margin down to zero or from an
|
||
margin up to overflow
|
||
Rationale: Enable to define a standard interface
|
||
Use Case: --
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋(RS_BRF_01904)
|
||
```
|
||
|
||
##### 6.1.3.3 [SRS_Frt_00032] Wrap around 应无需软件交互即可工作
|
||
|
||
```
|
||
Type: Valid
|
||
Description: --
|
||
Rationale: Save runtime. Don't make time 'walk' i.e. Interrupt consumes time
|
||
and thus adds time which is not tracked by the timer.
|
||
Use Case: Hardware timer shall be configured to run continuously. There
|
||
shall be no action necessary to restart the timer. Wrap around
|
||
shall load the restart value with support of HW: e.g. No additional
|
||
free running timer is available. A CapCom Timer shall be shared.
|
||
Its configuration is as follows: CapCom Timer starts at 0xFFFF,
|
||
reload margin value is 0x3ff, reload value is 0xFFFF, counter is
|
||
configured as down counter. After counting down to 0x3FF reload
|
||
0xFFFF without software interaction.
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋(RS_BRF_01904)
|
||
```
|
||
|
||
##### 6.1.3.4 [SRS_Frt_00033] 应有一个函数用于以原子方式读取定时器的值
|
||
|
||
```
|
||
Type: Valid
|
||
Description: This function reads timer ticks. The conversion of timer ticks to
|
||
time in SI units (seconds, milliseconds, microseconds,
|
||
nanoseconds) is not included.
|
||
Rationale: Avoid inconsistent access.
|
||
Use Case: The Timer value must be read consistent (even across byte
|
||
boundaries or more than one clock cycle). This may involve
|
||
protected access to 8bit-/16bit-/32bit-/64bit-registers:
|
||
For example Tricore TC1766 offers a timer width of 56 bit. These
|
||
56 bits may be accessed by TIM0 ... TIM6 Registers. Whereas
|
||
TIM0 reads ticks. TIM1 reads each 16th tick TIM2: 265th, TIM3:
|
||
4096th, TIM4: 65536th TIM5: 2^20th, TIM6: 2^32th. The registers
|
||
will provide consistency even over more than 32 bits if registers
|
||
are read in the HW-defined order
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904,RS_BRF_01056)
|
||
```
|
||
|
||
##### 6.1.3.5 [SRS_Frt_00047] SWFRT 应提供 "用户" 相关的 API（函数/宏）以将 ticks 转换为时间
|
||
|
||
```
|
||
Type: Valid
|
||
Description: This function has a number of ticks as a parameter and converts
|
||
its parameter to time in SI units (seconds, milliseconds,
|
||
microseconds, nanoseconds).
|
||
Rationale: Allow conversion to SI based time units.
|
||
Use Case: A) Peripheral devices need a start-up time before they may be
|
||
accessed. This start-up time is specified in the HW description.
|
||
A timeout [in SI Units] needs to be implemented to avoid
|
||
reading to non valid data. This timeout needs to be mapped a)
|
||
to a hw timer which could cope with the interval b) to a value
|
||
which gives the ticks of this timer
|
||
B) Diagnostics communication requires variable inter-frame
|
||
times (STMIN). They need to be set as a measure interval
|
||
which may be 100 µs up to 900 µ (9 values) and a second
|
||
measure interval of 1 ... 127 ms (126 values). These 135
|
||
values are to be calculated offline based on the available
|
||
timers and cyclic main functions.
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01056)
|
||
```
|
||
|
||
##### 6.1.3.6 [SRS_Frt_00034] 模块应提供计算先前存储值（作为参数传递）与当前定时器值之间经过的 ticks 的功能
|
||
|
||
```
|
||
Type: Valid
|
||
Description: The caller needs to provide the last read out value.
|
||
Rationale: Support different levels of functionality respectively code size and
|
||
execution time.
|
||
Use Case: Read the present timer value and use time from function in
|
||
parameter to calculate the difference
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01056)
|
||
```
|
||
|
||
#### 6.1.4 关闭操作
|
||
|
||
##### 6.1.4.1 [SRS_Frt_00041] SWFRT 不应被关闭
|
||
|
||
```
|
||
Type: Valid
|
||
Description: --
|
||
Rationale: There is nothing to shut down; not all timers can be stopped.
|
||
Use Case: --
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01096)
|
||
```
|
||
|
||
##### 6.1.4.2 [SRS_Frt_00048] SW FRT 功能应在其 Init 函数之后得到保证，在 ECU 的 'SLEEP'、'Wakeup I'、'StartUP I'、'Go OFF II' 和 'Power Off' 状态下不可用
|
||
|
||
```
|
||
Type: Valid
|
||
Description: The functionality will return undefined results in the above
|
||
states of ECU, therefore it shall not be used in these states.
|
||
Rationale: PLL might be not available / reduced etc.
|
||
Use Case: Do NOT use this functionality when there is the risk of unknown
|
||
timer settings.
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01104,RS_BRF_01096)
|
||
```
|
||
|
||
#### 6.1.5 故障操作
|
||
|
||
无特定需求。
|
||
|
||
### 6.2 非功能需求
|
||
|
||
#### 6.2.1 时间需求
|
||
|
||
无特定时间需求。
|
||
|
||
#### 6.2.2 资源使用
|
||
|
||
##### 6.2.2.1 [SRS_Frt_00044] SWFRT 不应阻塞定时器的使用
|
||
|
||
```
|
||
Type: valid
|
||
Description: Allow more than one module to use the same timer. If the other
|
||
modules requirements are in similar range the reuse of their
|
||
configuration shall be enabled.
|
||
Rationale: Enable the sharing of timers
|
||
Use Case: If a PWM works with a frequency which is in the range of the
|
||
SWFRT requirements this timer shall be offered for use.
|
||
Dependencies: --
|
||
Supporting Material: --
|
||
⌋( RS_BRF_01904, RS_BRF_01048)
|
||
```
|
||
|
||
---
|
||
|
||
## 7. 引用的 AUTOSAR 文档
|
||
|
||
- [1] Layered Software Architecture, AUTOSAR_EXP_LayeredSoftwareArchitecture.pdf
|
||
- [2] Glossary, AUTOSAR_TR_Glossary.pdf
|
||
- [3] Specification of GPT Driver, AUTOSAR_SWS_GPTDriver.pdf
|
||
- [4] Specification of Operating System, AUTOSAR_SWS_OS.pdf
|
||
- [5] Software Standardization Template, AUTOSAR_TPS_StandardizationTemplate.pdf
|
||
|
||
---
|
||
|
||
## 翻译说明
|
||
|
||
- **文档类型**：AUTOSAR SRS（Software Requirements Specification，软件需求规范）
|
||
- **翻译策略**：本 SRS 文档（19 页）规模适中，已进行完整翻译，包括所有功能需求、非功能需求、配置/初始化/运行/关闭/故障各阶段以及需求追溯表。
|
||
- **摘要标记位置**：
|
||
- 第 5 章需求追溯：表格已完整翻译（7 行）
|
||
- 文档较短，未使用"完整表见原文 PDF"摘要标记
|
||
- **保留内容**：
|
||
- 需求 ID（如 `SRS_Frt_00019`、`SRS_Frt_00030` 等）
|
||
- AUTOSAR 方框符 `⌈⌋`
|
||
- 所有 API 标识符、模块缩写
|
||
- 文档间交叉引用
|
||
- 定时器寄存器编号（Tricore TC1766 定时器说明）
|
||
- **术语对照表**：
|
||
- Free Running Timer → 自由运行定时器
|
||
- SWFRT → 软件自由运行定时器
|
||
- Wrap Around → 环绕
|
||
- Tick → 计时单位/刻度
|
||
- Resolution → 分辨率
|
||
- Range → 范围
|
||
- Continuous Mode → 连续模式
|
||
- GPT Timer → 通用目的定时器
|
||
- PLL → 锁相环
|
||
- Pre-scaler → 预分频器
|
||
- Atomic read → 原子读
|