ece-l304 lecture 6

ECE-L304 Lecture 6

Review of Step 5

Introduction to Step 6 and 7Final Lecture

Quiz Next Week

ECE-L304 Lecture 7 2

Up to now ADC is running

What is your sampling rate? DAC is running

What is your resolution? 555 Timer is running (or close to running)

What is the frequency and duty cycle?

The final stretch - What remains? Build 17 bit address generator for RAM

Using 2 8 bit counters + ? Build Control Circuitry to:

Take a reading on the ADC Store it to RAM Once RAM is filled, output recorded

waveform

Step 6 and 7 Prelab

Read the datasheets for the 74LS08 AND gate, 74LS112 JK flipflop, 74LS590 8-bit counter

Complete the Step 6 Prelab Worksheet Review RAM and ADC control logic

Project CircuitProgress to Date

ADC DAC

AddressGen

R/WControl

Project CircuitStep 7 Blocks

ADC DAC

AddressGen

R/WControl

ClockADC

Control

Step 6 Part 1

Assemble the 16-bit address generator Place the circuitry according to your floorplan Use the 555 counter as the clock for now

Design and build a circuit that will provide a 17th bit

This step is required to get full hardware credit Confirm functionality using the logic

analyzer

Step 674LS590 Description

8-Bit Counter With Register Parallel Register Outputs Choice Of 3 State Or Open Collector

Register Outputs Guaranteed Counter Freq DC To 20

Multi-chip applications “For cascading, a ripple carry output RCO is

provided. Expansion is easily accomplished for two stages by connecting RCO of the first stage to CCKEN of the second stage. Cascading for larger count chains can be accomplished by connecting RCO of each stage to CCK of the following stage.”

Step 6Cascaded 74LS590 Chips

CCLKEN

“Both the counter and register clocks are positive edge triggered. If the user wishes to connect both clocks together, the counter state will always be one count ahead of the register.”

Part 2 - Measure AND Time Delay Wire the clock signal into two AND gates in

series to create a delay Measure the delay and use this signal as the

input for your control circuitry Use the oscilloscope to measure delay by

placing the input and output signals on the screen simultaneously, trigger on the input signal and use the cursors to measure the delay between edges

Step 6 Prelab Analyze the control circuit used in the

Step 4 simulation

Qfrom AddressGenerator

TC = Terminal Count

Step 6 Prelab Graph the expected outputs

QQbarCLKRE (OE)WE0101010101

RE = Read EnableOE = Output EnableWE = Write Enable

Draw these curves

Step 6 Prelab In your Prelab Workbook

Sketch the schematic Sketch your control circuitry and timing

diagrams needed to control circuit

What should the circuit do? The circuit should have two stages

1- Take 2^17 readings from the ADC and store then in the RAM

2- Take the ADC offline and write the recorded signals from the RAM to the bus for output

Note - The ADC output and the RAM input/output are all on the same bus, meaning that the ADC cannot write outputs to the bus at the same time as the RAM

Part 3 - Control Circuitry First - decide which signals are involved in

the control circuitry 555 Timer ADC controls RAM controls

Second - create a timing diagram that describes what the signals need to look like in order to control the circuit properly

Board Center Connectors ADC Control

CS_, RD_, WR_, INTR_ Power, GND RAM Control

CE1_, CE2, OE_, WE_ RAM Addresses

A16 - A0

RAM Controls Subset of NEC RAM (uPD431000A) Control

Table:

We also have CS1 and CS2 to deal with

WE OE Mode L X WRITE H L READ

Active LowLogic

ADC Control Get the ADC off-line

Our acquisition system has only one data bus, which is shared by the ADC and the DAC

We have to take the ADC off-line during the RAM READ cycle so we do not have the ADC and RAM writing to the bus simultaneously

ADC Control Specify when to get new data

Take the ADC out of its current free-running mode

In free-running mode, the INTR pin signal initiates a new data conversion when it falls

Synchronize the system Generate a new memory address every clock

cycle Put new data on the bus every clock cycle

ADC ControlADC0804 Pins

CS = Chip SelectRD = ReadWR = WriteINTR = Interrupt

CLK IN

ADC ControlFree-Running Circuit

CS = Chip SelectRD = ReadWR = WriteINTR = Interrupt

20CSRDWRCLK ININTR

While CS is low, acquisition starts whenever WR drops

How can this happen? Start switch is

grounded INTR output falls

20CSRDWRCLK ININTR

While CS and RD are low, data will appear at the outputs [DB7:DB0] as soon as it is ready About 72 internal

clock cycles

20CSRDWRCLK ININTR

Rising transition on WR begins the conversion

100 ns min

RD must be low for data to appear at outputs. When RD is high, outputs are Hi-Z.

ADC Control Redesign the connections to the ADC

control pins to get the results you want Details of the pin functions are on the data

sheet Diagrams of control sequences are on the

data sheet

The first task is to make sure the 555 clock and the ADC internal clock are coordinated.

If WE_ never rises, no conversions will occur.

If there are no conversions, INTR_ will stay high.

There should be no pulses on WR_ in READ mode.

When RD_ is high the ADC output is high-impedance.

OE_ is low in READ mode.

Draw a Timing Diagram for the Control Circuitry Which signals are involved Which ones are inputs and which are outputs What should the signals look like in order to

get the correct behavior Try writing the sequence of steps down in

words first, then creating the timing diagram Keep in mind which signals are active low

and active high, what state does a signal need to be in during a stage where it is not switching?

Timing Diagram Complete a timing diagram and circuit

schematic for the controls Have Eric check your results before you

begin construction, and be ready to answer questions about your decisions

Hints Don’t connect power supplies

incorrectly now, if your RAM goes you will not be happy

Remove your ADC chip during control signal testing

Check your ADC internal clock - is it fast enough?

Optimizing the Circuit Goal: Record audio to your specs Storage is limited

131,072 sites in RAM (217) Acquisition speed is limited

ADC internal clock must make about 72 cycles per conversion

High speed = high bandwidth High speed = short capture time

Optimize the Circuit You have a design goal for how you

want your circuit to function If necessary to meet this goal:

Adjust the ADC internal clock frequency Adjust the on-board (555) clock

Test the Circuit Display analog input (sine or ramp) and

analog output on scope During the RAM WRITE cycle, the data on

the bus comes from the ADC The DAC automatically converts it back to

analog. At low frequencies, the DAC output should

be identical to the analog input

Test the Circuit Display analog input (sine or ramp) and

analog output on scope During the RAM READ cycle, the data on

the bus comes from the RAM The DAC automatically converts it back to

analog The DAC output should be identical to the

analog input of the previous acquisition cycle

Test the Circuit Note the length of the acquisition (WRITE)

cycle. Does it equal 131,072 times the period of the on-board clock?

Note the length of the READ cycle. Does it equal 131,072 times the period of the on-board clock?

If you want to see if the circuit is really working, pull the RAM chip Your output should be 0 during the READ cycle

Experimental Results

Deliverables Test 1 - Bandwidth

Analog in, analog out Determine failure frequency

A = (Goal - Measured)/Goal A ≤ 0 (measured exceeds goal) 20 pts 0.95 ≤ A < 1 18 pts 0.90 ≤ A < 0.95 16 pts A < 0.90 14 pts

Deliverables Test 2 - Address Generator

Working 17 bits 20 pts Working 17 bits, novel design 22 pts Working 16 bits 16 pts < 16 bits 10 pts

Deliverables Test 3 - RAM/ADC Control

Working and in sync 20 pts Working not in sync 15 pts Not working 10 pts

Deliverables Test 4 - Timing

ADC internal clock period INTR period 555 timer period Record time Playback time

Deliverables Test 4 - Timing

For record time: R = (Calculated - Measured)/Calculated If R ≥ 0.9 10 pts If R < 0.9 5 pts

Deliverables Test 5 - Playback

Is DAC output from stored data? Yes 20 pts No 10 pts

Deliverables Test 6 - Construction

Has the circuit been constructed neatly and with a reasonable floorplan?

0 to 10 pts

Deliverables Test 7 - Return Board

Has the circuit been returned in good condition?

Good Condition multiplier = 1.0 Damaged multiplier = 0.8 Not Returnedmultiplier = 0.0

Deliverables Write up your control design:

Design criteria what were the specs you wanted sketch the desired output waveforms

Sketch the control schematic Show any equations used, and define

terms if necessary

Deliverables Write up your control design:

Discuss what changes were made to the circuit to optimize performance

How effective were they? Document the performance change

Deliverables Have your circuit functionality verified Comment on your observations and

provide conclusions on the entire experiment

Any improvements to this Step? Any improvement to the lab course?

Yes, we do have class next week

Quiz Next Week ADC operation

Sampling rate vs internal clock Resolution

DAC Resolution

Wire Wrapping Basic Instrument Operation Quiz will be in Bossone 303 starting at 6pm

and ending at 6:45pm promptly, no exceptions

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