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```International Journal of Electronics,
Communication & Instrumentation Engineering
Research and Development (IJECIERD)
ISSN(P): 2249-684X; ISSN(E): 2249-7951
Vol. 4, Issue 2, Apr 2014, 137-148
© TJPRC Pvt. Ltd.

THE USE OF MICROSOFT EXCEL TO SIMULATE THE CHARGING CAPACITOR (C)
THROUGH A RESISTANCE (R), AND CALCULATING THE APPROPRIATE VALUE OF T
(RC) OF 8051 MICROCONTROLLER RESET CIRCUIT

DAHLAN RP SITOMPUL & POLTAK SIHOMBING

University of North Sumatera (USU) and ATI Immanuel, Faculty of Computer Science and Information Technology,

Medan, North Sumatra, Indonesia

ABSTRACT

On this occasion, the author would like to discuss the use of Microsoft Excel to simulate the charging of the
capacitor (C) through a resistance (R) of the 8051 microcontroller reset circuits m . The author would also shows the
equation (rule of thumb) to calculate the appropriate value of t (RC) used to form the 8051 microprocessor reset circuit and
using the table and the graph obtained from Microsoft Excel to opt the proper RC value.

KEYWORDS: 8051 Microprocessor Reset Circuits, TTL (Transistor Transistor Logic) Voltage Range

INTRODUCTION

Due to a lot of student that forwarded inquiries at my microprocessor / microcontroller class and electronics
enthusiasts on the blog [31 asked technique or method to calculate the values of the resistor and capacitor of microcontroller
8051 reset circuits has inspired the authors to carry out this research (literature Study). To master the method of
determining the value of these two components, an understanding of the working principle of charging and discharging the
capacitor through a resistance is highly required (DC voltage source). It will not only help the students of how to calculate
the capacitor and resistor values of microcontroller reset circuits, but will also provide a basis for them to understand other
subjects such as Electrical, Analog Electronics, Digital Electronics, Microprocessor / microcontroller. Computers and other
electronics studies. The authors hope this paper will contribute to science, especially in helping the teacher or lecturer to
teach and facilitate students to comprehend the working principle of charging a capacitor through a resistance of 8051
microprocessor reset circuit.

Main

The figure below shows the block diagram of the reset circuits of the microprocessor 805 1 system.

+5V +5V

+5V +5V

(1) Power-on Reset Circuit and (2) With Manual Reset Option

www.CircuitsToday.com

Figure 1: The Types of Reset Circuits of Microcontroller 8051 [2]

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Dahlan Rp Sitompul & Poltak Sihombing

A 8051 Microprocessor will be in a reset state if pin 9 (RESET pin) see figure 1 above gets a 5 V DC voltage
(Active High) for at least 2 MCs (MC-Machine Cycle) 14111511191 .

System Clock

K ONE MACHINE CYCLE H

STATE6 STATE1 STATE2 STATE3 STATE4 STATES STATE6 STATE1

| P2 | PI | P2 | PI | P2 | PI | P2 | PI | P2 | PI | P2 | PI | P2 I PI | P2 |

“jinnnnnnnnnnnnnnni

ALE |

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Figure 2: MC-Machine Cycle 141

Figure 2 above shows a machine cycle, it can be seen from the figure that a machine cycle consists of six states
(State 1 -State 6) and each state consists of two pulses (PI and P2), each pulse (P) is a full cycle of the oscillator (clock) 141 .
In other words, a machine cycle consists of 12 pulses of oscillator (clock); a single machine cycle is the minimum time
required to perform an instruction of 8051 microcontroller 115111 J , several instructions require more than one machine cycle
(2 and 4) to complete them 11611171 . In general an instruction of 8051 microcontroller requires only one machine cycle
(12 clock pulses), but some instructions require 2 Machine Cycles and two instructions take 4 Machine Cycles
(MUL AB and DIV AB) 1171 to finish their work [16I[1?1 . From the above discussion we can see that to put 8051
microprocessor in a valid reset state we must connect pin 9 of the 8051 microprocessor to a 5 Volt DC voltage source for at
least 24 oscillator cycles (P) or 2 Machine Cycles, 2 X 12 oscillator cycles [4][131 . The period of the oscillator cycle (P)
depends on the type of crystal used in the oscillator circuits. A 12 MHz crystal is generally used, but for application in
associated with serial data communications a 11.0592 MHz crystal should be used 1411151 . In this study we will use the 12
MHz crystal oscillator; you can do the same calculation for a 11.0592 MHz crystal oscillator as for 12 MHz crystal
oscillator.

For crystal oscillator with a frequency of 12 MHz (12 x 10 6 Hz) there will be 12 million (12 X 10 6 ) pulses per

1 6 6

second. Thus the period (T) of one pulse is — X 10 s (seconds), therefore the period of one machine cycle is 10

12

1 6

seconds (1 u sec); 12 X — X 10 seconds. As it has been mentioned before in order to enter the valid reset state, the 8051

12

microcontroller pin 9 (reset) has to be connected to 5 volts (Vcc) for > 2 p sec (2 Machine Cycles) 141 . This term of time > 2
p sec (2 Machine Cycles) will be used by the author as one of the requirements for calculating the appropriate value of R
and C of 8051 microcontroller reset circuits.

There are two types of reset of the 8051 microprocessor, known as power on reset and manual reset see
figure l [2][l51 . Power on reset occurs when microprocessor gets either a DC voltage of 5 Volt from a battery or other source
of DC voltage; voltage source with a regulator that can maintain a 5 V (DC) output voltage such as the FM7805 191 . While
the manual reset, reset will occur when the reset button is pressed [4] .

Impact Factor (JCC): 4.9467

Index Copernicus Value (ICY): 3.0

The Use of Microsoft Excel to Simulate the Charging Capacitor (C) through a Resistance (R),
and Calculating the Appropriate Value of T (RC) of 8051 Microcontroller Reset Circuit

139

To analyze the 805 1 microcontroller reset circuit in Figure 1 above, we can redraw it as shown in figure 3 below
with assumption that input impedance of the 8051 microcontroller is infinite; 8051 Microcontroller does not load the reset
circuits.

Vcc (5V)

Figure 3: Microprocessor 8051 Reset Circuits

From Electricity and basic electronics course we know that the equation for charging the capacitor through a
resistor can be written as equation 1 below [7I[8I[1SI .

Vc = V( 1-e t/RC )

(i)

And from KVL (Kircoff Voltage Law) we know that

V=VC + VR

and

VC=V —VR

If we apply the distributive law of multiplication over subtraction on equation 1 we will get

yc=v-i/^ c

And from equations 3 and 4 we can see that the voltage across the resistor (R) is

VR =Ve

t/ RC

(5)

We will use equation 1 and equation 5 in Microsoft Excel to depict the graph of VC and VR (Voltage on C and R
consecutively) versus time (seconds) as shown in Figure 4 below (t = RC = 1 second, and Vcc = 5V).

t = RC with unit of second (s) is the time taken by the capacitor (C) to charge and achieve a voltage of 63% of the
source voltage (3.2 V) and for the resistor ( R ) to drop from Vcc to 37% (1.8 V) of the source voltage (Vcc) if the voltage
source is 5 V 1 ' 81 .

When 5 Volt DC voltage source has not been connected to Vcc of 8051 microcontroller system, Vcc voltage will
be at 0 Volts so does the voltage on the capacitor and resistor (VR + VC = Vcc), the capacitor will have a total discharge
m . However when 5 Volt DC voltage source connected to the 8051 microcontroller system, pin 40 (Vcc) will get 5 Volt

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DC voltage and pin 20 (GND) will get Ground (0 Volt) from the power supply, the voltage on the capacitor will initially be
at 0 volts and the voltage of the resistor will be at 5 volts (Vcc = VR + VC) and so does the voltage on pin 9 (reset) will get
the same voltage of 5 volts; cause the system microcontroller will enter the reset state. According to equation 1 the voltage
on the capacitor will increase slowly from 0 Volts (the speed of capacitor charging will depend on RC value) over time
toward 5 volts and reverse voltage development will occur across the resistor as equation 5 shows; it will go down or drop
to 0 volts from 5 Volts which will cause the microcontroller to enters the normal state (not in the reset state) when a
threshold voltage low (1.2 V) is reached, see figure 4 below.

Figure 4: The Graph of Voltage Across C and R Vs Time (t (R X C)=l Second)

When the manual reset key, see figure 1 is pressed, a voltage of 5 Volts (DC) will be at the RST pin (pin 9) of the
8051 microcontroller and will be back soon (within a period of 0.1 seconds) to a voltage of 0 volts when the key is
released 1611141 .

On Reset

Figure 5: Manual Reset of 8051 Microcontroller 1141

When entering a reset state (manual reset) the contents of the internal RAM will not be interrupted, the contents of
the PC (program counter) is removed and filled with OOh, bank 0 register is selected as the default bank register, (SP) Stack
Pointer will be initialized to 07h, and all ports (port 0-port 3) will be filled with OFFh [4] . In practice the 8051 voltage logic
is in the TTL (transistor transistor logic) voltage range 1151 , threshold voltage of 8051 microcontroller is between 1.1 V to
1.3 V 1?1 ;input voltage below that voltage is considered to be a logic 0 voltage, and voltage above that voltage is considered
as a logic 1 voltage. Thus the microcontroller will be in the reset state when the voltage on pin 9 (reset) is still at about 1.2
V (average of 1.1 V and 1.3 V), the voltage on the capacitor C is 3.8 V.

Impact Factor (JCC): 4.9467

Index Copernicus Value (ICV): 3.0

The Use of Microsoft Excel to Simulate the Charging Capacitor (C) through a Resistance (R), 141

and Calculating the Appropriate Value of T (RC) of 8051 Microcontroller Reset Circuit

The author will use this threshold voltage of 1.2 V across R (3.8 V voltages on capacitor C) as the key point in
calculating the appropriate value of the capacitor and resistor of the 8051 Microcontroller 8051 reset circuit.

We can use equation 5 to determine the value of R and C in accordance with the requirements (the valid reset
conditions to occur) as mentioned above; oscillator and power supply are in stable condition, and the reset pin should be
maintained at 5 Volts for 24 clock cycles (2 p sec) period of time. Oscillator will be stable after 1 ms and the power supply
will be stable after 10 ms [201 ; after switching the power supply voltage on.

From equation 5 we get that

VR

V

-t/RC

= e

(6)

And,

T f VR \ T f ~ t/RC \

Cn( ) = Rn( e )

V

(7)

Then, we can write that.

/.//(

VR

V

)

— t

RC

( 8 )

r

From equation 8 we can determine the value of the corresponding RC. Ln( ) will result in a negative value.

r

If we put VR = 1.2 V and V=5V, then Ln{ ) will be -1,427 thus equation 8 can be rearranged into

1,427 = —

RC

(9)

As discussed earlier, when the power supply is turned on reset circuit will maintain the state of the reset pin high
(1) for some time; duration of the reset pin in a high state is determined by the value of R and C of the reset circuit.

To guarantee the valid reset to occur [201 , the reset pin must be maintained in a high state (5 Volts) for a long enough time to
ensure oscillator in a start-up state (1ms), the power supply to be stable (10 ms) plus a 2-Machine Cycle (2p sec) then from
equation 9 to ensure a valid reset state to occur we choose t> 100 m S then we can opt the equation for determining the
appropriate value of the RC as follows [?I ,

RC>\ 00ms ( ] 0 )

The combination of the value of R = 10 K O, and C = lOpF will give RC = 100 ms. Reset circuits of R = 8K2Q
and C = 10 pF is widely used in various applications of microcontroller 8051 will give RC = 82 ms.

The graph below shows the simulation results of the voltage across the resistor for various values of t (RC);
lms, 10 ms, 20 ms, 40 ms, 80ms, and 160 ms.

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V

>_

So 3 -

"5

>

\

\

■■■ VR2(V)

\

VR3(V)

VR4(V)

1 -

>0

o 4

L.

5

0

1C

)0

Time (

m

15

>)

0

2C

)0

2.

Figure 6: Graph of Voltage across R vs. Time for Some RC Values
(1 ms, 10 ms, 20 ms, 40 ms, 80 ms, and 160 ms) [10][11]

the

Table 1 below is used to depict the graphs in Figure 6. The formula for VR1, VR2, VR3, VR4, VR5, and VR6 are

-t/lms T ^ _ —t/lOms - _ —t / 20ms -t /40ms

following consecutively. VR\ — 5e VR2 — 5e VR3 — 5e VR4 — 5e

VR5 = 5e

—t I80ms

, and

VR6 = 5e

—t /160ms

Table 1: Voltage across R VS Time for Various Values of RC (1ms, 10 ms, 20 ms, 40 ms, 80 ms, Dan 160 ms) [1#I[111

t (ms)

VR1 (V)

VR2(V)

VR3(V)

VR4(V)

VR5(V)

VR6(V)

0

5

5

5

5

5

5

1

1,839397

4,524187

4,756147

4,87655

4,937889

4,968847

2

0,676676

4,093654

4,524187

4,756147

4,87655

4,937889

3

0,248935

3,704091

4,30354

4,638717

4,815972

4,907123

4

0,091578

3,3516

4,093654

4,524187

4,756147

4,87655

5

0,03369

3,032653

3,894004

4,412485

4,697065

4,846166

6

0,012394

2,744058

3,704091

4,30354

4,638717

4,815972

7

0,004559

2,482927

3,52344

4,197285

4,581094

4,785966

8

0,001677

2,246645

3,3516

4,093654

4,524187

4,756147

9

0,000617

2,032848

3,188141

3,992581

4,467987

4,726514

10

0,000227

1,839397

3,032653

3,894004

4,412485

4,697065

11

8.35E-05

1,664355

2,884749

3,797861

4,357672

4,6678

12

3.07E-05

1,505971

2,744058

3,704091

4,30354

4,638717

13

l,13E-05

1,362659

2,610229

3,612637

4,25008

4,609816

14

4.16E-06

1,232985

2,482927

3,52344

4,197285

4,581094

15

l,53E-06

1,115651

2,361833

3,436446

4,145146

4,552552

16

5.63E-07

1,009483

2,246645

3,3516

4,093654

4,524187

17

2.07E-07

0,913418

2,137075

3,268849

4,042802

4,495999

18

7.61E-08

0,826494

2,032848

3,188141

3,992581

4,467987

19

2,8E-08

0,747843

1,933705

3,109425

3,942984

4,440149

20

1.03E-08

0,676676

1,839397

3,032653

3,894004

4,412485

21

3.79E-09

0,612282

1,749689

2,957777

3,845632

4,384992

22

1.39E-09

0,554016

1,664355

2,884749

3,797861

4,357672

23

5.13E-10

0,501294

1,583184

2,813524

3,750683

4,330521

24

1.89E-10

0,45359

1,505971

2,744058

3,704091

4,30354

25

6.94E-11

0,410425

1,432524

2,676307

3,658078

4,276727

26

2.55E-11

0,371368

1,362659

2,610229

3,612637

4,25008

27

9,4E-12

0,336028

1,296201

2,545782

3,56776

4,2236

Impact Factor (JCC): 4.9467

Index Copernicus Value (ICV): 3.0

The Use of Microsoft Excel to Simulate the Charging Capacitor (C) through a Resistance (R),
and Calculating the Appropriate Value of T (RC) of 8051 Microcontroller Reset Circuit

143

Table 1: Contd.,

28

3.46E-12

0.30405

1.232985

2,482927

3,52344

4,197285

29

1.27E-12

0.275116

1,172851

2,421623

3,479672

4,171134

30

4.68E-13

0.248935

1,115651

2,361833

3,436446

4,145146

31

1.72E-13

0.225246

1,06124

2,303519

3,393758

4,119319

32

6.33E-14

0.203811

1,009483

2,246645

3,3516

4,093654

33

2,33E-14

0.184416

0,96025

2,191175

3,309966

4,068148

34

8.57E-15

0.166866

0,913418

2,137075

3,268849

4,042802

35

3.15E-15

0.150987

0,86887

2,08431

3,228243

4,017613

36

1,16E-15

0.136619

0,826494

2,032848

3,188141

3,992581

37

4,27E-16

0.123618

0,786186

1,982657

3,148537

3,967705

38

1.57E-16

0.111854

0,747843

1,933705

3,109425

3,942984

39

5.77E-17

0.10121

0,71137

1,885962

3,070799

3,918418

40

2.12E-17

0.091578

0,676676

1,839397

3,032653

3,894004

41

7,81E-18

0.082863

0,643675

1,793982

2,994981

3,869742

42

2.87E-18

0.074978

0,612282

1,749689

2,957777

3,845632

43

1.06E-18

0.067843

0,582421

1,706489

2,921035

3,821672

44

3.89E-19

0.061387

0,554016

1,664355

2,884749

3,797861

45

1.43E-19

0.055545

0,526996

1,623262

2,848914

3,774198

46

5.27E-20

0.050259

0,501294

1,583184

2,813524

3,750683

47

1.94E-20

0.045476

0,476846

1,544095

2,778574

3,727314

48

7.13E-21

0.041149

0,45359

1,505971

2,744058

3,704091

49

2.62E-21

0.037233

0,431468

1,468789

2,709971

3,681013

50

9.64E-22

0.03369

0,410425

1,432524

2,676307

3,658078

51

3.55E-22

0.030484

0,390408

1,397155

2,643062

3,635286

52

1.31E-22

0.027583

0,371368

1,362659

2,610229

3,612637

53

4.8E-23

0.024958

0,353256

1,329015

2,577804

3,590128

54

1.77E-23

0.022583

0,336028

1,296201

2,545782

3,56776

55

6.5E-24

0.020434

0,319639

1,264198

2,514158

3,545531

56

2,39E-24

0.018489

0,30405

1,232985

2,482927

3,52344

57

8.79E-25

0.01673

0,289222

1,202542

2,452083

3,501488

58

3,24E-25

0.015138

0,275116

1,172851

2,421623

3,479672

59

U9E-25

0.013697

0,261699

1,143894

2,391541

3,457991

60

4.38E-26

0.012394

0,248935

1,115651

2,361833

3,436446

61

1.61E-26

0.011214

0,236795

1,088105

2,332494

3,415036

62

5.93E-27

0.010147

0,225246

1,06124

2,303519

3,393758

63

2,18E-27

0.009182

0,214261

1,035038

2,274904

3,372613

64

8.02E-28

0.008308

0,203811

1,009483

2,246645

3,3516

65

2.95E-28

0.007517

0,193871

0,984558

2,218737

3,330718

66

1.09E-28

0.006802

0,184416

0,96025

2,191175

3,309966

67

3.99E-29

0.006155

0,175422

0,936541

2,163956

3,289343

68

l,47E-29

0.005569

0,166866

0,913418

2,137075

3,268849

69

5.4E-30

0.005039

0,158728

0,890865

2,110527

3,248482

70

1.99E-30

0.004559

0,150987

0,86887

2,08431

3,228243

71

7.31E-31

0.004126

0,143623

0,847417

2,058418

3,208129

72

2,69E-31

0.003733

0,136619

0,826494

2,032848

3,188141

73

9.9E-32

0.003378

0,129956

0,806088

2,007596

3,168277

74

3.64E-32

0.003056

0,123618

0,786186

1,982657

3,148537

75

1.34E-32

0.002765

0,117589

0,766775

1,958028

3,12892

76

4.93E-33

0.002502

0,111854

0,747843

1,933705

3,109425

77

1.81E-33

0.002264

0,106399

0,729379

1,909684

3,090052

78

6.67E-34

0.002049

0,10121

0,71137

1,885962

3,070799

79

2,45E-34

0.001854

0,096274

0,693807

1,862534

3,051667

80

9.02E-35

0.001677

0,091578

0,676676

1,839397

3,032653

81

3.32E-35

0.001518

0,087112

0,659969

1,816548

3,013758

82

1.22E-35

0.001373

0,082863

0,643675

1,793982

2,994981

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Table 1: Contd.,

83

4.49E-36

0.001243

0,078822

0,627782

1,771697

2,976321

84

1.65E-36

0.001124

0,074978

0,612282

1,749689

2,957777

85

6.08E-37

0.001017

0,071321

0,597165

1,727954

2,939348

86

2.24E-37

0.000921

0,067843

0,582421

1,706489

2,921035

87

8.23E-38

0.000833

0,064534

0,568041

1,68529

2,902835

88

3.03E-38

0.000754

0,061387

0,554016

1,664355

2,884749

89

1,1 IE-38

0.000682

0,058393

0,540337

1,64368

2,866776

90

4.1E-39

0.000617

0,055545

0,526996

1,623262

2,848914

91

1.51E-39

0.000558

0,052836

0,513985

1,603098

2,831164

92

5.54E-40

0.000505

0,050259

0,501294

1,583184

2,813524

93

2.04E-40

0.000457

0,047808

0,488917

1,563517

2,795995

94

7.5E-41

0,000414

0,045476

0,476846

1,544095

2,778574

95

2.76E-41

0,000374

0,043258

0,465072

1,524914

2,761262

96

1.02E-41

0,000339

0,041149

0,45359

1,505971

2,744058

97

3.74E-42

0,000306

0,039142

0,442391

1,487264

2,726961

98

1.37E-42

0,000277

0,037233

0,431468

1,468789

2,709971

99

5.06E-43

0,000251

0,035417

0,420815

1,450543

2,693086

100

1.86E-43

0,000227

0,03369

0,410425

1,432524

2,676307

101

6.84E-44

0,000205

0,032047

0,400292

1,414729

2,659632

102

2.52E-44

0,000186

0,030484

0,390408

1,397155

2,643062

103

9.26E-45

0,000168

0,028997

0,380769

1,379799

2,626594

104

3.41E-45

0,000152

0,027583

0,371368

1,362659

2,610229

105

1.25E-45

0,000138

0,026238

0,362199

1,345732

2,593966

106

4.61E-46

0,000125

0,024958

0,353256

1,329015

2,577804

107

1.7E-46

0,000113

0,023741

0,344534

1,312506

2,561743

108

6.24E-47

0,000102

0,022583

0,336028

1,296201

2,545782

109

2.3E-47

9.23E-05

0,021482

0,327731

1,2801

2,529921

110

8.44E-48

8.35E-05

0,020434

0,319639

1,264198

2,514158

111

3.11E-48

7.56E-05

0,019437

0,311747

1,248494

2,498493

112

1.14E-48

6.84E-05

0,018489

0,30405

1,232985

2,482927

113

4.2E-49

6.19E-05

0,017588

0,296543

1,217668

2,467457

114

1.55E-49

5.6E-05

0,01673

0,289222

1,202542

2,452083

115

5.69E-50

5.07E-05

0,015914

0,282081

1,187604

2,436805

116

2.09E-50

4.58E-05

0,015138

0,275116

1,172851

2,421623

117

7.7E-51

4.15E-05

0,014399

0,268323

1,158282

2,406535

118

2.83E-51

3.75E-05

0,013697

0,261699

1,143894

2,391541

119

1.04E-51

3.4E-05

0,013029

0,255237

1,129684

2,37664

120

3.83E-52

3.07E-05

0,012394

0,248935

1,115651

2,361833

121

1.41E-52

2.78E-05

0,011789

0,242789

1,101792

2,347117

122

5.19E-53

2.52E-05

0,011214

0,236795

1,088105

2,332494

123

1.91E-53

2.28E-05

0,010667

0,230948

1,074589

2,317961

124

7.02E-54

2.06E-05

0,010147

0,225246

1,06124

2,303519

125

2.58E-54

1.86E-05

0,009652

0,219685

1,048057

2,289167

126

9.5E-55

1.69E-05

0,009182

0,214261

1,035038

2,274904

127

3.5E-55

1.53E-05

0,008734

0,208971

1,02218

2,26073

128

1.29E-55

1.38E-05

0,008308

0,203811

1,009483

2,246645

129

4.73E-56

1.25E-05

0,007903

0,198779

0,996943

2,232647

130

1.74E-56

1.13E-05

0,007517

0,193871

0,984558

2,218737

131

6.4E-57

1.02E-05

0,007151

0,189084

0,972328

2,204913

132

2.36E-57

9.25E-06

0,006802

0,184416

0,96025

2,191175

133

8.67E-58

8.37E-06

0,00647

0,179863

0,948321

2,177523

134

3.19E-58

7.58E-06

0,006155

0,175422

0,936541

2,163956

135

U7E-58

6.85E-06

0,005854

0,171091

0,924907

2,150473

136

4.31E-59

6.2E-06

0,005569

0,166866

0,913418

2,137075

137

1.59E-59

5.61E-06

0,005297

0,162746

0,902071

2,12376

Impact Factor (JCC): 4.9467

Index Copernicus Value (ICY): 3.0

The Use of Microsoft Excel to Simulate the Charging Capacitor (C) through a Resistance (R),
and Calculating the Appropriate Value of T (RC) of 8051 Microcontroller Reset Circuit

145

Table 1: Contd.,

138

5.84E-60

5.08E-06

0,005039

0,158728

0,890865

2,110527

139

2,15E-60

4,59E-06

0,004793

0,154809

0,879799

2,097378

140

7.9E-61

4,16E-06

0,004559

0,150987

0,86887

2,08431

141

2.91E-61

3,76E-06

0,004337

0,147259

0,858076

2,071324

142

1.07E-61

3.4E-06

0,004126

0,143623

0,847417

2,058418

143

3.93E-62

3.08E-06

0,003924

0,140077

0,83689

2,045593

144

1.45E-62

2,79E-06

0,003733

0,136619

0,826494

2,032848

145

5.32E-63

2,52E-06

0,003551

0,133245

0,816228

2,020183

146

1.96E-63

2,28E-06

0,003378

0,129956

0,806088

2,007596

147

7.21E-64

2,06E-06

0,003213

0,126747

0,796075

1,995088

148

2.65E-64

l,87E-06

0,003056

0,123618

0,786186

1,982657

149

9.75E-65

l,69E-06

0,002907

0,120566

0,77642

1,970304

150

3.59E-65

l,53E-06

0,002765

0,117589

0,766775

1,958028

151

l,32E-65

l,38E-06

0,002631

0,114685

0,75725

1,945829

152

4,86E-66

l,25E-06

0,002502

0,111854

0,747843

1,933705

153

1.79E-66

l,13E-06

0,00238

0,109092

0,738553

1,921657

154

6.57E-67

l,03E-06

0,002264

0,106399

0,729379

1,909684

155

2,42E-67

9.28E-07

0,002154

0,103772

0,720318

1,897786

156

8.89E-68

8.39E-07

0,002049

0,10121

0,71137

1,885962

157

3,27E-68

7,6E-07

0,001949

0,098711

0,702534

1,874211

158

1.2E-68

6.87E-07

0,001854

0,096274

0,693807

1,862534

159

4.43E-69

6.22E-07

0,001763

0,093897

0,685188

1,850929

160

1.63E-69

5.63E-07

0,001677

0,091578

0,676676

1,839397

161

5.99E-70

5.09E-07

0,001596

0,089317

0,668271

1,827937

162

2.2E-70

4,61E-07

0,001518

0,087112

0,659969

1,816548

163

8,1 IE-71

4,17E-07

0,001444

0,084961

0,651771

1,80523

164

2,98E-71

3,77E-07

0,001373

0,082863

0,643675

1,793982

165

1.1E-71

3,41E-07

0,001306

0,080817

0,635679

1,782805

166

4,04E-72

3,09E-07

0,001243

0,078822

0,627782

1,771697

167

1.49E-72

2,79E-07

0,001182

0,076876

0,619984

1,760659

168

5.46E-73

2,53E-07

0,001124

0,074978

0,612282

1,749689

169

2,01E-73

2,29E-07

0,00107

0,073127

0,604676

1,738787

170

7,39E-74

2,07E-07

0,001017

0,071321

0,597165

1,727954

171

2,72E-74

l,87E-07

0,000968

0,06956

0,589747

1,717188

172

IE-74

l,69E-07

0,000921

0,067843

0,582421

1,706489

173

3.68E-75

l,53E-07

0,000876

0,066168

0,575186

1,695856

174

l,35E-75

l,39E-07

0,000833

0,064534

0,568041

1,68529

175

4,98E-76

l,26E-07

0,000792

0,062941

0,560984

1,67479

176

1.83E-76

l,14E-07

0,000754

0,061387

0,554016

1,664355

177

6.74E-77

l,03E-07

0,000717

0,059871

0,547134

1,653986

178

2,48E-77

9,3E-08

0,000682

0,058393

0,540337

1,64368

179

9,13E-78

8.42E-08

0,000649

0,056951

0,533625

1,633439

180

3,36E-78

7,61E-08

0,000617

0,055545

0,526996

1,623262

181

l,24E-78

6.89E-08

0,000587

0,054174

0,52045

1,613149

182

4.54E-79

6.23E-08

0,000558

0,052836

0,513985

1,603098

183

l,67E-79

5.64E-08

0,000531

0,051531

0,5076

1,59311

184

6,15E-80

5,lE-08

0,000505

0,050259

0,501294

1,583184

185

2,26E-80

4,62E-08

0,000481

0,049018

0,495067

1,57332

186

8.32E-81

4,18E-08

0,000457

0,047808

0,488917

1,563517

187

3.06E-81

3,78E-08

0,000435

0,046628

0,482844

1,553776

188

1, 13E-8 1

3,42E-08

0,000414

0,045476

0,476846

1,544095

189

4,14E-82

3.1E-08

0,000393

0,044354

0,470922

1,534474

190

1.52E-82

2,8E-08

0,000374

0,043258

0,465072

1,524914

191

5.61E-83

2,53E-08

0,000356

0,04219

0,459295

1,515413

192

2,06E-83

2,29E-08

0,000339

0,041149

0,45359

1,505971

www.tjprc.org

editor@tjprc.org

146

Dahlan Rp Sitompul & Poltak Sihombing

Table 1: Contd.,

193

7.59E-84

2.08E-08

0,000322

0,040133

0,447955

1,496588

194

2.79E-84

1.88E-08

0,000306

0,039142

0,442391

1,487264

195

1.03E-84

1.7E-08

0,000291

0,038175

0,436895

1,477997

196

3.78E-85

1.54E-08

0,000277

0,037233

0,431468

1,468789

197

1.39E-85

1.39E-08

0,000264

0,036314

0,426108

1,459637

198

5.11E-86

1.26E-08

0,000251

0,035417

0,420815

1,450543

199

1.88E-86

1.14E-08

0,000239

0,034543

0,415588

1,441505

200

6.92E-87

1.03E-08

0,000227

0,03369

0,410425

1,432524

201

2.55E-87

9.33E-09

0,000216

0,032858

0,405327

1,423599

202

9.36E-88

8.44E-09

0,000205

0,032047

0,400292

1,414729

203

3.45E-88

7.63E-09

0,000195

0,031255

0,395319

1,405914

204

1.27E-88

6.91E-09

0,000186

0,030484

0,390408

1,397155

205

4.66E-89

6.25E-09

0,000177

0,029731

0,385559

1,38845

206

1.72E-89

5.66E-09

0,000168

0,028997

0,380769

1,379799

207

6.31E-90

5.12E-09

0,00016

0,028281

0,376039

1,371202

208

2.32E-90

4.63E-09

0,000152

0,027583

0,371368

1,362659

209

8.54E-91

4.19E-09

0,000145

0,026902

0,366755

1,354169

210

3.14E-91

3.79E-09

0,000138

0,026238

0,362199

1,345732

211

1.16E-91

3.43E-09

0,000131

0,02559

0,357699

1,337347

212

4.25E-92

3.1E-09

0,000125

0,024958

0,353256

1,329015

213

1.56E-92

2.81E-09

0,000119

0,024342

0,348868

1,320734

214

5.75E-93

2.54E-09

0,000113

0,023741

0,344534

1,312506

215

2.12E-93

2.3E-09

0,000107

0,023155

0,340254

1,304328

216

7.79E-94

2.08E-09

0,000102

0,022583

0,336028

1,296201

217

2.86E-94

1.88E-09

9.7E-05

0,022025

0,331853

1,288125

218

1.05E-94

1.7E-09

9.23E-05

0,021482

0,327731

1,2801

219

3.88E-95

1.54E-09

8.78E-05

0,020951

0,32366

1,272124

220

1.43E-95

1.39E-09

8.35E-05

0,020434

0,319639

1,264198

221

5.25E-96

1.26E-09

7.94E-05

0,019929

0,315669

1,256321

222

1.93E-96

1.14E-09

7.56E-05

0,019437

0,311747

1,248494

From the discussion, table 1 and figure 6 above several points can be drawn as conclusions, such as,

• The value of RC is made in such a way as to make sure to obtain the valid duration of reset (reset pin is
maintained in a high state for 2 machine cycles or 24 clock cycles (2 p seconds), waiting for the oscillator to
stabilize ini ms and for the power supply to be stable in 10 ms)

• RC value of 1 ms is too short, and will lead to failure to achieve a valid reset state; voltage VR = 1.2 is reached
(reset occurs) in just 1.427 ms

• For RC = 80 ms reset (VR = 1.2 V) will be reached in about 1 15 ms

• For RC = 160 ms reset (VR = 1.2 V) will be accomplished in about 222 ms; too long

• Equation 10 is good enough to determine the value of RC, it can guarantee the achievement of a valid reset state
of 805 1 microcontroller

CONCLUSIONS

This paper is expected to contribute to science, particularly in the areas of Microprocessor, Computer, Analog
Electronics, and Digital Electronics. And it can be used as a media for teaching and learning process that will make it
easier for student to comprehend the subject and the teacher or lecturer to carry out the teaching process better.

Impact Factor (JCC): 4.9467

Index Copernicus Value (ICY): 3.0

The Use of Microsoft Excel to Simulate the Charging Capacitor (C) through a Resistance (R),
and Calculating the Appropriate Value of T (RC) of 8051 Microcontroller Reset Circuit

147

REFERENCES

2. http://www.circuitstoday.com/wp-content/uploads/201 1/12/805 l-reset-circuit.jpg

3. http://www. 805 lprojects.net/t 17721 -pO/proiect-help/proiect-help-needed.htm#post 17739

4. http://www.circuitstodav.com/8051-microcontroller

5. http://www.atmel.com/Images/doc4284.pdf

6. http://www.pirc.com/tech/8051/board5/reset and crystal.html

7. http://hillside.net/europlop/HillsideEurope/Papers/EuroPLoP1999/1999 Pont DesigningAndImplementing.pdf

8. http://www.nhu.edu.tw/~chun/BE-Chl l-Capacitor%20Charging%20&%20Discharging. pdf

10. http://office.microsoft.com/en-us/excel-help/modeling-exponential-growth-HA001 1 1 1888.aspx

11. http://www.ehow.com/how 4486593 use-excels-exp-function.html

12. http://grok.lsu.edu/article.aspx?articleid=7094

13. http://www.mikroe.com/chapters/view/65/chapter-2-8051-microcontroller-architecture/

14. http://www.mikroe.com/img/publication/8051-books/programming-8051-mcu/chapter/ch2/52.gif

15. http://www.freewebs.com/maheshwankhede/basic.html

16. http://www.8052.com/tuttimng.phtml

18. http://www.electronics-tutorials.ws/rc/rc 1 .html

19. http://www.atmel.com/Images/doc4284.pdf

classsearchhighlight8051span-user-classsearchhighlightmanualspan.html

(Intel 8051 manual) page 200/334

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```