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ELEC2630 EMBEDDEDELEC2630 EMBEDDED

SYSTEMS THEORYSYSTEMS THEORY

Lecture 3: Asynchronous dataLecture 3: Asynchronous data

laboratory & Introduction tolaboratory & Introduction to

Micro-controller internalsMicro-controller internals

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Asynchronous Data LabsAsynchronous Data Labs

Laboratories designed to investigate the

process of serial communication using the

RS232 interface as an example.

Investigate the use of an interface in an

unusual way to create an input or output

device for an embedded system.

Use other semiconductor devices that can

be useful in embedded system design.

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RS232 Interface deviceRS232 Interface device

The function of the device is to change the 0

to +5 Volt logic levels from the circuit to

the +12 Volt to -12 Volt logic levels of RS

232.

The other section of the chip changes the

+12 Volt to -12 Volt from the RS232

interface into the 0 to +5 Volts for astandard logic level circuit. [This includes

most Micro-controller chips]

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ASYNCH WAVEFORMASYNCH WAVEFORM

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LAB 1: Tests of asynchronousLAB 1: Tests of asynchronousserial input deviceserial input device

Vary the resistor connected to theMonostable and note the differentcharacters that are displayed on Terminal.

For each character record the pulse widththat generated it.

The resistance of the variable needed to

generate the pulse. Settings of Terminal to display the

characters.

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Design of input deviceDesign of input device

If resistance for each character isrepresented by R1, R2, R3, R4 and R5 withR5 being the largest.

Work out the change of resistance betweencharacters. Ra = (R1 - 0)

Rb = (R2 - R1)

Rc = (R3 R2) Rd = (R4 R3)

Re = (R5 - R4)

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Wafer Switch DesignWafer Switch Design

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LAB 2: Asynchronous serialLAB 2: Asynchronous serialoutput deviceoutput device

Inverted serial input from PC via RS232interface used to remove reset from astableclock generator during logic low signal.

Inverted serial input also triggers amonostable via short pulse derived via aCR differentiator

Monostable then resets a four bit counter After reset, counter counts pulses from

clock until serial line signal goes high again

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LAB 2: Test of asynchronousLAB 2: Test of asynchronousoutput deviceoutput device

With terminal at 9600 baud, send thefollowing 5 characters.

~ | x p and note for each character

The pulse width of the serial input and thenumber on the four bit counter output.

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Report RequirementsReport Requirements

Brief outline of Build and test for LAB1 andLAB2

Results for LAB1 and LAB2

Conclusions, i.e. why the particularcharacter was produced in LAB1 or whythe particular number was observed on

the counter for the character input inLAB2.

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Introduction to Micro-computerIntroduction to Micro-computerinternalsinternals

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Problems with traditionalProblems with traditionalarchitecturearchitecture

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Problems (continued)Problems (continued)

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