HW4soln-3750-F08

HW4soln-3750-F08 - EE 3750 HW 4 solutions 1 EE 3750...

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EE 3750 — HW 4 solutions 1 EE 3750 — Homework 4 solutions Fall 2008 1. (a) Brey, Chapter 9, Problem 25 - What is the purpose of the demultiplexed BHE signal on the 8086 microprocessor? (b) Brey, Chapter 9, Problem 32 - Briefly describe the purpose of each T state listed: (a) T1, (b) T2, (c) T3, (d) T4. (a) The BHE (bus high enable) signal indicates that the microprocessor is transferring data through data bus connections D15-D8. (b) (a) State T1 is used by the microprocessor to provide the memory or I/O with the address. (b) State T2 provides access time to the memory and also is where the READY input is sampled. (c) State T3 is where the data are sampled or sent to the memory or I/O. (d) State T4 is used to deactivate the control signals. 2. Write an 8086 instruction sequence to use program-controlled I/O to input words and store the negative-valued words into array under . Input a total of 200 words. Let indev denote the input device. The status port for indev is a byte port at address 4CC2H; bit 3 is the ready bit. The data port for indev is a word port at address 4CC4H. STATUS EQU 4CC2H DATA EQU 4CC4H READY EQU 1000B MOV CX, 200 ; loop counter MOV DI, 0 ; pointer in under TOP: MOV DX, STATUS ; use DX because addresses longer than 8 bits CKIN: IN AL, DX ; poll status TEST AL, READY JZ CKIN MOV DX, DATA IN AX, DX ; input data when ready CMP AX, 0 JGE MORE MOV UNDER[DI], AX ; store negative-valued inputs ADD DI, 2 MORE: LOOP TOP
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EE 3750 — HW 4 solutions 2 3. Write an 8086 instruction sequence to work with a simple alarm system using program-controlled I/O. The alarm system receives inputs from a keypad, a door, and a window; it sends outputs to an alarm. Each input and output is to be a single byte, except for the output to
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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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HW4soln-3750-F08 - EE 3750 HW 4 solutions 1 EE 3750...

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