ELEC4601 Microprocessor systems Lab 3 Tutorial

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ELEC4601 Microprocessor systemsLab 3 Tutorial
Interrupts

• October 29 November 02, 2007

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Comments

• NEW NEW NEW NEW NEW NEW NEW NEW
• Unable to maintain lab section - 5 marks
• Will be strictly followed
• unless you have a hard copy of permission.
• All group members should understand the lab. TAs
  will ask you questions after the lab. Individual
  marks will vary depending on your level of
  understanding.
• Prelab must be done BEFORE lab starts.

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Objectives Interrupts

• 1) Understand Interrupts and their use in a
  microprocessor-based system
• An interrupt results in the transfer of control
  to a new program location.
• What is the sequence of operations that occur
  during an interrupt?
• What are the signals that appear on the bus
  during an interrupt cycle?
• What is the Interrupt Vector Table and how is it
  used?

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Objectives Interrupt Controller (8259A)

• 2) Understand the Programmable Interrupt
  Controller (8259A) and its interface to the 8086
  on the SDK Board
• What are the key signals that connect the 8259A
  to the 8086?
• What is the Interrupt Mask Register and how is
  it used?
• How are interrupt priorities handled using the
  8259A?
• Study ICW1, ICW2, ICW4, OCW1, OCW2.

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Objectives Timer (8253)

• 3) Understand the Programmable Interval Timer
  (8253)
• What is the 8253, and how is it used?
• How is the 8253 connected to the 8086 and the
  8259A (review Appendix B)
• How are the counters initialized and loaded?
• What signals are used to clock the counters?
• Do all counters use the same clock? (review the
  diagram in Appendix B)

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Objectives Parallel Port (8255A) and Keyboard
Display Controller (8279)

• 4) Understand the Parallel Ports chip (8255A)
• How can the 8255A be used to interface the 8086
  to a D/A Converter (review Lab 2)
• 5) Understand the Keyboard Display Controller
  (8279)
• How do you write to display RAM using the 8279?
• How can you address the 7-segment LEDs on the
  SDK-86?

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Reference Materials for Prelab

• From your class notes
• Communication Between I/O and CPU (pages
  122-124)
• From the Peripherals Handbook
• Read about the 8253, 8255, 8259, and the 8279
• From the 8086 Hardware Reference Manual
• Read the section on interrupts.
• Look up information for the LDS, XLAT, STI, and
  CLI commands

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Block Diagram of Timer 8253
CLK0
IR0
IR1
Counter 0 ????H
Counter 1 ????H
IR2
PCLK
CLK1
2.45 MHz
Counter 2 ????H
CLK2
Timer 8253
PIC 8259

• Counter 0 has data of 5FB4H24500d, what is the
  period for CLK0?
• 10 ms
• What is the data needed in counter 0 to get a
  period of 0.1 ms?
• F5 H 245 d

Read Appendix B
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Part A Prelab

• Review the code in lab3A.asm
• Fill in the blank comments beside the given code
  in provided spaces
• 8255 Setup
• CNTR_8255 EQU 0FFFEH Port control address
• OUTPUT_MODE EQU 0B5H Set up mode for port B
  output
• 8253 Setup
• COUNT_CNTR EQU 000EH counter control register
  address
• MODE2 EQU 74H _________________________________
  _
• MODE3 EQU 36H _________________________________
  _
• COUNT0 EQU 0008H counter0 address
• COUNT1 EQU 000AH counter1 address
• LOPT1MSEC EQU 0F5H _____________________________
  _____
• HIPT1MSEC EQU 00H _____________________________
  _____

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Part A Overview

• Download Lab3A.asm to the SDK (masm, link,
  exe2hex) and run it (sdk, GO FE000. L G)
• Understand what is happening.
• Hint This program initializes a couple of
  counters, then runs in an infinite loop
• Monitor the bus signals in the Logic Analyzer
  and copy INTR, /INTA waveforms from into your lab
  procedure handbook
• Answer the questions in your report

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Seven Segment Display Table

• What you need to display 0?
• a, b, c, d, e, f
• Hex 3F
• What you need to display 1?
• b, c
• Hex 06
• LED_TABLE DB 3FH 0
• DB 06H 1
• ...
• How can you use it? - LDS, XLAT

h
a
b
c
d
e
f
g
h
Bits
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Part B Prelab

• Review the code in lab3B.asm and comment the code
  in the blanks provided (as part A)
• Write the code section to implement ISR2 which is
  timed using COUNT2 (counter 2)
• Write LED_TABLE for 0-9 (use it in ISR2)
• Print out and bring your commented code to the
  lab
• Find out how can you set ISR2 to run at highest
  priority?

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Part B Overview

• Download Lab3B.asm given on the web to the SDK
  and run it as it is (do not modify yet).
• This program generates a sawtooth waveform on
  the D/A converter and outputs a GARBAGE character
  to the rightmost digit of the SDK-86 display
  every second. Make sure it works properly before
  you modify the code
• If everything works fine, modify Lab3B.asm
  according to your code to enable interrupt (ISR2)
  that generates a counter (0-9) in the leftmost
  digit of the SDK-86 display. The counter should
  count down from 9 to 0 and decrement every 0.5
  seconds.
• Your new code must not interfere with the
  sawtooth or the GARBAGE character routines.

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More Hints

• What was the code for Lab1 part D?
• Understand the use and syntax of LDS, XLAT,
  LED_TABLE
• Study spec. of ICs 8259, 8253, 8255, 8279
• Understand the timer block diagram (8253)
• Accessing ports (control and data registers)