图4 时钟策略

3.4.1 睡眠和唤醒

置位命令寄存器的进入睡眠位（BasicCAN ）模式或模式寄存器（PeliCAN模式）的睡眠模式位后，如果没有总线活动和中断等待，SJA1000就会进入睡眠模式。振荡器在15个CAN位时间内保持运行状态。此时,微型控制器用CLKOUT频率来计时，进入自己的低功耗模式。如果出现三个唤醒条件之中的一个[1]，振荡器会再次启动并产生一个唤醒中断。振荡器稳定后，CLKOUT频率被激活。

3.5 CPU接口

SJA1000支持直接连接到两个著名的微型控制器系列：80C51和68xx。通过SJA1000的MODE引脚可选择接口模式：

Intel模式： MODE 高 Motorola模式： MODE 低

地址/数据总线和读/写控制信号在Intel模式和Motorola模式的连接如图5所示。Philips基于80C51系列的8位微控制器和XA结构的16位微型控制器都使用Intel 模式。

为了和其他控制器的地址数据总线和控制信号匹配，必须要附加逻辑电路。但是必须确保在上电期间不产生写脉冲。另一个方法在这个时候使片选输入是高电平，禁能CAN 控制器。

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图5 SJA1000的CPU时钟接口

3.6 物理层接口

为了和PCA82C200兼容,SJA1000包括一个模拟接收输入比较器电路。如果收发器的功能由分立元件实现，就要用到这个集成的比较器。

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图6 SJA1000的接收输入比较器

如果使用外部集成收发器电路，而且没有在时钟分频寄存器里使能比较器旁路功能，RX1输出要被连接到2.5V 的参考电压（现有的收发器电路参考电压输出）。图6显示了两种设置的相应电路：CBP=激活和CBP=非激活另外唤醒信号的通道被下拉对于使用集成的收发器电路的所有新应用我们建议激活（使用）SJA1000的比较器旁路功能（图7）。如果这个功能被使能，施密特触发器的输入有效，内部的传 播延迟tD2比接收比较器的延迟tD1要小得多。它对最大的总线长度[6]有正面的影响。另外，休眠模式的电流将显著降低。

图7 带有集成收发器电路的标准应用

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附件2：外文原文（复印件）

SJA1000 Stand-alone CAN controller

1. INTRODUCTION

The SJA1000 is a stand-alone CAN Controller product with advanced features for use in automotive and general industrial applications. It is intended to replace the PCA82C200 because it is hardware and software compatible. Due to an enhanced set of functions this device is well suited for many applications especially when system optimization, diagnosis and maintenance are important.

This report is intended to guide the user in designing complete CAN nodes based on the SJA1000. The report provides typical application circuit diagrams and flow charts for programming.

2. OVERVIEW

The stand-Operation:

- BasicCAN Mode (PCA82C200 compatible) - PeliCAN Mode

Upon Power-up the BasicCAN Mode is the default mode of operation. Consequently, existing hardware and software developed for the PCA82C200 can be used without any change. In addition to the functions known from the PCA82C200 [7], some extra features have been implemented in this mode which make the device more attractive. However, they do not influence the compatibility to the PCA82C200.

The PeliCAN Mode is a new mode of operation which is able to handle all frame types according to CAN specification 2.0B [8]. Furthermore it provides a couple of enhanced features which makes the SJA1000 suitable for a wide range of applications. 2.1 CAN Node Architecture

Generally each CAN module can be divided into different functional blocks. The

connection to the CAN bus lines is usually built with a CAN Transceiver optimized for the applications [3], [4], [5]. The transceiver controls the logic level signals from the CAN controller into the physical levels on the bus and vice versa.

The next upper level is a CAN Controller which implements the complete CAN protocol defined in the CAN Specification [8]. Often it also covers message buffering and acceptance filtering.

All these CAN functions are controlled by a Module Controller which performs the functionality of the application. For example, it controls actuators, reads sensors and

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