電子信息專業(yè)畢業(yè)設(shè)計(jì)外文資料翻譯--sja1000獨(dú)立的can控制器應(yīng)用指南-電子信息-資料下載頁(yè)
2025-05-11 20:53本頁(yè)面
【導(dǎo)讀】有一系列先進(jìn)的功能適合于多種應(yīng)用，特別在系統(tǒng)優(yōu)化、診斷和維護(hù)方面非常重要。本文是要指導(dǎo)用戶設(shè)計(jì)基于SJA1000的完整的CAN節(jié)點(diǎn)。BasicCAN模式是上電后默認(rèn)的操作模式。因此，用PCA82C200開(kāi)發(fā)的已有硬件。和軟件可以直接在SJA1000上使用，而不用作任何修改。PeliCAN模式是新的操作模式，它能夠處理所有規(guī)范的幀類型。它還提供一些增強(qiáng)功能使SJA1000能應(yīng)用于更寬的領(lǐng)域。通常，每個(gè)CAN模塊能夠被分成不同的功能塊。化的CAN收發(fā)器連接到CAN。收發(fā)器控制從CAN控制器到總線物理層或相反的邏輯電。多數(shù)情況下這個(gè)控制器是一個(gè)集成電路。根據(jù)CAN規(guī)范，CAN核心模塊控制CAN幀的發(fā)送和接收。所有收到的報(bào)文由驗(yàn)收濾波器驗(yàn)收并存儲(chǔ)在接收FIFO。因?yàn)閿?shù)據(jù)超載可能性被大大降低，這使用戶能。SJA1000的片選由微控制器的。引腳17的外部復(fù)位信號(hào)要同步并被內(nèi)部延長(zhǎng)到15個(gè)tXTAL。蕩器在15個(gè)CAN位時(shí)間內(nèi)保持運(yùn)行狀態(tài)。振蕩器穩(wěn)定后，CLKOUT頻率被激活。是必須確保在上電期間不產(chǎn)生寫(xiě)脈沖。發(fā)器的功能由分立元件實(shí)現(xiàn)，就要用到這個(gè)集成的比較器。
【正文】 et which results in 1,33 MHz in this case. Sleep and Wakeup 12 Upon setting the Go To Sleep bit in the Command Register (BasicCAN mode) or the Sleep Mode bit in the Mode Register (PeliCAN mode) the SJA1000 will enter Sleep Mode if there is no bus activity and no interrupt is pending. The oscillator keeps on running until 15 CAN bit times have been passed. This allows a microcontroller clocked with the CLK OUT frequency to enter its own low power consumption mode. If one of three possible wakeand a Wakeup interrupt is generated. As soon as the oscillator is stable the CLK OUT frequency is active. CPU Interface The SJA1000 supports the direct connection to two famous microcontroller families: 80C51 and 68xx. With the MODE pin of the SJA1000 the interface mode is selected. Intel Mode: MODE = high Motorola Mode: MODE = low The connection for the address/data bus and the read/write control signals in both Intel and Motorola mode is shown in Figure 5. For Philips 8bit microcontrollers based on the 80C51 family and the 16bit microcontrollers with XA architecture the Intel Mode is used. For other controllers additional glue logic is necessary for adaptation of the address/data bus and the control signals. However, it has to be made sure that no write pulses are generated during powerup. Another possibility is to disable the CAN controller with a highlevel on the chip select input in this time. 13 Physical Layer Interface For patibility purposes with the PCA82C200, the SJA1000 includes an analog receive input parator circuit. This integrated parator can be used if the transceiver function is realized with discrete ponents. If an external integrated transceiver circuit is used and the parator bypass function is not enabled in the Clock Divider Register, the RX1 input has to be connected to a reference voltage of (reference voltage output of existing transceiver circuits). Figure 6 shows the equivalent circuits for both configurations: CBP = active and CBP = inactive. Additionally the path for the wakeup signal is drawn. For all new applications where an integrated transceiver circuit is used, it is remended to activate the parator bypass function of the SJA1000 (Figure 7). If this function is enabled, a schmitttrigger input is used and the internal propagation delay tD2 is much shorter as the delay tD1. of the receive parator. This has a positive impact on the maximum bus length [6]. Additionally, it will reduce the supply current in sleep mode significantly.
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