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ECE3120: Chapter 7- Parallel Ports Interfacing with Simple I

. PrevBasic concepts of I/OOverview of Parallel portsTodayInterfacing with output devices. Electrical Characteristic Consideration for I/O Interfacing. When interfacing I/O device to the MCU, one needs to consider electrical compatibility issues.There are two electrical compatibility issue

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ECE3120: Chapter 7- Parallel Ports Interfacing with Simple I

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    1. ECE3120: Chapter 7- Parallel Ports Interfacing with Simple I/O Devices Dr. Xubin He http://iweb.tntech.edu/hexb Email: hexb@tntech.edu Tel: 931-3723462, Brown Hall 319

    2. Prev… Basic concepts of I/O Overview of Parallel ports Today… Interfacing with output devices

    3. Electrical Characteristic Consideration for I/O Interfacing When interfacing I/O device to the MCU, one needs to consider electrical compatibility issues. There are two electrical compatibility issues: Voltage level compatibility Current drive capability There are many IC technologies in use. Some are bipolar, whereas others are unipolar (mainly CMOS and BICMOS). Voltage parameters related to electrical compatibility Input high voltage (VIH) Input low voltage (VIL) Output high voltage (VOH) Output low voltage (VOL)

    4. For Device X to Drive Device Y Correctly The output high voltage of device X (VOHX) must be higher than the input high voltage of device Y (VIHY). The output low voltage of device X (VOLX) must be lower than the input low voltage of device Y (VILY). The input and output voltage levels of several popular logic families are shown in Table 7.3. At the same power supply level, the CMOS device has no problem in driving the bipolar and CMOS devices. Bipolar devices have problem in driving CMOS devices. HCS12 cannot be driven by bipolar devices. Bipolar devices have problems driving CMOS devices (including HCS12).

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