Redesign the circuit of Problem using a 74HC85 magnitude comparator. Add a \"cop
ID: 2084435 • Letter: R
Question
Redesign the circuit of Problem using a 74HC85 magnitude comparator. Add a "copy overflow" feature that will activate an ALARM output if the OPERATE output fails to stop the machine when the requested number of copies is done. Below Figure shows the block diagram of a logic circuit used to control the number of copies made by a copy machine. The machine operator selects the number of desired copies by closing one of the selector switches S1 to s9. This number is encoded in BCD by the encoder and is sent to a comparator circuit. The operator then hits a momentary-contact START switch, which clears the counter and initiates a HIGH OPERATE output that is sent to the machine to signal it to make copies. As the machine makes each copy, a copy pulse is generated and fed to the BCD counter. The counter outputs are continually compared with the switch encoder outputs by the comparator. When the two BCD numbers match, indicating that the desired number of copies has been made, the comparator output X goes LOW, this causes the OPERATE level to return LOW and stop the machine so that no more copies are made. Activating the START switch will cause this process to be repeated. Design the complete logic circuitry for the comparator and control sections of this system. I have no idea about this problem. Please solve this problem.Explanation / Answer
The BCD-to-binary function of the analo-gous to the algorithm:
b. Shift right, examine, and correct after each shift until the least significant decade contains a number smaller than eight and all other converted decades contain zeros.
In addition to BCD-to-binary conversion, is programmed to generate BCD 9's complement or BCD 10's complement. Again, in each case, one bit of the comple-ment code is logically equal to one of the BCD bits; there-fore, these complements can be produced on three lines. As outputs are not required in the BCD-to-bi-nary conversion, they are utilized to provide these comple-ment codes as specified in the function table when the de-vices are connected as shown.
BINARY-TO-BCD CONVERTERS
The function performed by these 6-bit binary-to-BCD con-verters is analogous to the algorithm:
Symbol
Parameter
Min
Nom
Max
Units
VCC
Supply Voltage
4.75
5
5.25
V
VIH
High Level Input Voltage
2
V
VIL
Low Level Input Voltage
0.8
V
VOH
High Level Output Voltage
5.5
V
IOL
Low Level Output Current
12
mA
TA
Free Air Operating Temperature
0
70
§C
'184 and '185A Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted
Symbol
Parameter
Conditions
Min
Typ
Max
Units
(Note 1)
VI
Input Clamp Voltage
VCCe Min, IIe b12 mA
b1.5
V
ICEX
High Level Output
VCCe Min, VOe 5.5V
100
mA
Current
VILe Max, VIHe Min
VOL
Low Level Output
VCCe Min, IOLe Max
0.4
V
Voltage
VIHe Min, VILe Max
II
Input Current @ Max
VCCe Max, VIe 5.5V
1
mA
Input Voltage
IIH
High Level Input Current
VCCe Max, VIe 2.4V
25
mA
IIL
Low Level Input Current
VCCe Max, VIe 0.4V
b1
mA
ICCH
Supply Current with
VCCe Max
65
95
mA
Symbol
Parameter
Min
Nom
Max
Units
VCC
Supply Voltage
4.75
5
5.25
V
VIH
High Level Input Voltage
2
V
VIL
Low Level Input Voltage
0.8
V
VOH
High Level Output Voltage
5.5
V
IOL
Low Level Output Current
12
mA
TA
Free Air Operating Temperature
0
70
§C
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