aLec17_locals_LCD - Introduction to Embedded Microcomputer...

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Introduction to Embedded Microcomputer Systems Lecture 17.1 Jonathan W. Valvano Recap Local variables: scope and allocation How these concepts apply to C Binding, allocation, access, deallocation Overview I/O synchronization LCD interface Implementing local variables with a stack frame Parameter passing Blind Cycle Counting Synchronization Blind cycle counting is appropriate when the I/O delay is fixed and known. This type of synchronization is blind because it provides no feedback from the I/O back to the computer. Busy Waiting Synchronization Check busy/ready flag over and over until it is ready Interrupt Synchronization Request interrupt when busy/ready flag is ready Synchronizing with an input device Blind Cycle Wait a fixed time Read data Busy-Wait Status Read data Busy Ready Interrupt Fifo Get data from Fifo Empty Ready Read data Put data in Fifo return from interrupt Synchronizing with an output device Blind Cycle Wait a fixed time Write data Busy-Wait Status Write data Busy Ready Interrupt Fifo Put data into Fifo Full Idle Write data Get data from Fifo return from interrupt Fifo Empty 8.5. Parallel Port LCD interface with the HD44780 controller Vss (ground) Vdd (power) Vee (contrast) RS R/W E DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 +5 9S12 1 by 16 LCD display PH0 PH1 PH2 PP0 PP1 PP2 PP3 PP4 PP5 PP6 PP7 HD44780 controller 5 by 8 bit font 10k Ω Figure 8.13. Interface of a HD44780 LCD controller.
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This note was uploaded on 09/19/2010 for the course E E 16280 taught by Professor Valvano during the Fall '10 term at University of Texas.

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aLec17_locals_LCD - Introduction to Embedded Microcomputer...

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