Chapter 11

Chapter 11 - I/O Interfacing May be classified as Isolated...

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Unformatted text preview: I/O Interfacing May be classified as: Isolated I/O; Memory mapped I/O. Instructions: IN accumulator, source; OUT destination, accumulator. Basic I/O Interfaces Deboucing Mechanical switches bounce when they are actuated. A circuit is needed to ensure that the output of the switch provides a single transition upon the switch actuation, instead of a sequence of transitions. This circuit is called a debouncer. Port Example 16 bits output port decoded at addresses 40H and 41H. It used two latches (74ALS374) and a 16L8 used to decode the addresses. Intel 82C55 - PPI The Intel 82C55 programmable peripheral interface is a low cost device that allow the user 24 I/O connections which may be grouped in different ways with up to three different modes of operation. Intel 82C55 - PPI Programming the Intel 82C55T The 82C55 is programmed by sending a command byte to the control register. This command byte defines how the 82C55 will work. It defines the mode of operation and which ports are input or output. 8 Digit LED Display Example 20481 LCD Display Example 4 lines by 20 characters display that accepts ASCII code as data. Few connections necessary for operation: 8 data; 3 control; R/W’(1=read,0=write) RS(1=data,0=command) E(1=enabled) Commands are defined in table 11-3 of text. Keyboard Interface Example Stepper Motor Interface Example Rotation is accomplished in full or half steps. Full steps sequence: 33H, 66H, 0CCH, 99H Half step sequence: 11H, 33H, 22H, 66H, 44H, 0CCH, 88H, 99H. ...
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This note was uploaded on 01/25/2012 for the course EE 3750 taught by Professor Desouza during the Fall '08 term at LSU.

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Chapter 11 - I/O Interfacing May be classified as Isolated...

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