ELEC4601 Microprocessors Lab 2 Tutorial Signal Waveforms and Parallel port programming

Reading Materials From your class notes: –Pin-outs and Pin Functions (pages 66-70) –Bus Buffering and Latching (page 72) –Bus Timing (pages ) From the SDK-86 manual: –OB (Output Byte) Command (page 3-15) From the Peripherals Handbook: –8255A (starting on page 3-100, specifically page ) From the 8086 Hardware Reference Manual: –Look up commands OUT, MOV and JMP (For # of clock cycles, numbers in brackets are for 186)

Pre-lab For your Pre-Lab: –Calculate the number of clock cycles expected in the program fragment of part A (page Lab#2-4) –Find Control Byte value (part B step 1) –Write the program (part B step 4) Further study (from Lab Manual): –Read Appendix A, logic analyzer operation –Read Appendix B, in particular the 8255A and DAC extensions

SIGNAL WAVEFORMS Part A

Objectives Understand bus cycles / timing What do the ALE, WR and RD bits indicate? Can you tell what is the happening during each clock cycle by looking at ALE, WR, RD and contents of the bus? Instruction pre-fetching, and the effect of JMP on the instruction queue

Logic analyzer view (incorrect!)

Pre-lab  Calculate the number of cycles the program segment should take to execute (page Lab#2-4) Lab2.asm available on the course web

Procedure 1.Run the program (lab2.asm) –Infinite loop that continuously moves data from register to memory 2.Monitor bus signals during program execution –Logic Analyzer will show the signals (20 bit address/data, WR, RD, ALE, PCLK) –Show the Analyzer waveform to a TA to verify 3.Draw the waveforms on the timing diagram in lab manual (Show your work. Rest of part A can be done after the lab) 4.Interpret what is happening at each clock cycle (Table 1) 5.Explain what is happening on the bus during program execution (Q. 5-8)

PARALLEL PORT PROGRAMMING Part B

Objectives Understand how to set up 8255A I/O port Understand how to output values to the port Understand how to determine control word to configure the port Understand how the D/A converter works Write a program using this information to produce a sawtooth waveform –You should be able to adjust the period and amplitude of your waveform by adjusting your code

DA converter concept  D/A converter produces converts digital value to analogue Each data byte you output to D/A converter will produce a certain constant voltage level Your code will have to make the output a continuous (?) sawtooth waveform  Voltage levels linearly related to data values (which range from 00H to FFH)  Demonstrate your waveform to TA 1.Ramp from your pre-lab code 2.Modification you made later o/p voltage 7F 0 V

Part B: Pre-Lab  Determine the control word needed for part B  Write the program for Part B (name it lab2b.asm) Try to optimize your coding  Know how you can adjust the amplitude and period  M odify program

Part B: Procedure Program the I/O port for certain output –8255A: I/O component is used to interface to CPU –Control register is used to configure ports –Use OB (output byte) command from keypad to output to ports –Use OUT command in your program to do the same Use this port to send data values to the D/A converter Find data values that produce specified voltage levels –You will use an oscilloscope to view the D/A output –Your should be able to calculate certain data value needed for certain output voltage

See you next week!