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Saturday, January 28, 2012

AOI Logic With Integrated Circuits (74LSXX)



Bunch of Integrated Circuits
  "AOI Logic" stands for And Or Inverter Logic. Invert is also referred to as a NOT gate because it outputs the opposite logical value of its input. In a NOT gate, when the input pin is connectied to +3V (logic high) then the output pin becomes attached to 0V (logic low). Resource Links, see bottom of post!



"So then, What is the 74 Series?" 
The 74 Series is a large set of Integrated Circuits (IC). Integration Circuits are space saving, fast, and pre-built mini circuits encapsulated in a bit of black plastic. ICs are also refered to as "chips".


Our Focus Today and Probably the Most Basic Of The 74 Series IC chips... 
The AND, OR, and NOT gated IC Chips (74xx08, 74xx32, 74xx04)


Reading Chips Can Be Difficult
The 74 Series chips have VERY confusing labels such as: "SN74HC04" or "MC74S02" + tons more...
   When reading the chips you need to look for where it says "74" and then skip to the next set of numbers on that same line where a second number will appear.

74xx08 is 4 AND gates in one chip (2 input : 1 output per gate)
74xx32 is 4 OR gates in one chip (2 input : 1 output per gate)
74xx04 is 6 NOT gates in one chip (1 input 1 output per gate)

All three, 74xx08, 74xx32, 74xx04 integrated circuits (IC) have 14 metal pins oriented into two parallel lines, 7 on both lines (2*7=14 of course!).


PIN LABELS FOR YA!
So, the 74 series chips like most integrated circuits (IC) do not have any pin labels; but this doesn't mean all hope is lost!
All 74 series chips have what is called a "data sheet" online in various locations for professional usage reference, but since we are not professionals I will explain the data sheet for the 74xx08, 74xx32, 74xx04 (AOI) chips.
74xx08
{ PIN1 = input1A;   PIN2 = input1B;   PIN3 = output1C;
  PIN4 = input2A;   PIN5 = input2B;   PIN6 = output2C;
 PIN7 = Ground (GND);   PIN10 = input3A;   PIN9 = input3B;
  PIN8 = output3C;   PIN13 = input4A;   PIN12 = input4B;
 PIN11 = output 4C;   PIN14 = Power (PWR) }

The Quad (4-gated) AND chip, 74xx08, has two pins for ground and power that must be hooked up properly for the chip to do its logic calculations. If you locate a dip or dot (or both even) on one side of the 74xx08 chip that is the "top" where the left-top pin is called pin 1 and the top-right pin is called pin 14. Pin 14 (top-right corner pin) is the POWER PIN. You need to supply
 the chip with from 4V to 9V of voltage through pin 14. *Same goes for the power set up for the 74xx32 and 74xx04 (inverter).

A 74LS08N chip (74xx08)

The logic function of an AND gate is to OUTPUT TRUE ONLY if BOTH input is a logic high (true/on).

AND Truth Table
A B C
0 0 1
1 0 1
0 1 0
0 0 1
AND gate chip (74xx08) Resources:
Commercial Sale: AND Gates (74xx08)

TAKE NOTE: PIN 14 IS POWER (TOP RIGHT + NEXT TO TOP INDICATOR DOT or DIP ON CHIP). This is true for the 74xx04 (inverter gates IC) and the 74xx32 (OR gates IC).



74xx32 (OR gate IC chip)

The Quad (4-gated) OR chip, 74xx32, has two pins for ground and power that must be hooked up properly for the chip to do its logic calculations just like the 74xx08 (AND gated IC). If you locate a dip or dot (or both even) on one side of the 74xx32 chip that is the "top" where the left-top pin is called pin 1 and the top-right pin is called pin 14. Pin 14 (top-right corner pin) is the POWER PIN. You need to supply the chip with from 4V to 9V of voltage through pin 14.  *Exact same power hook up as 74xx08 and 74xx04
74S32N chip
OR Truth Table
A B C
1 0 1
1 0 1
0 1 1
0 0 0


The logic function of an OR gate is that the OUTPUT of an OR gate will be TRUE, the logic high (1) if atleast one input is a logic high (1). The 1 represents a point in a circuit with positive voltage. The 0 represents a point in a circuit with negative voltage (GND).



The Hex Inverter (6 inverter gates) NOT chip, 74xx04, has two pins for ground and power that must be hooked up properly for the chip to do its logic calculations just like the 74xx08 (AND gated IC) and the 74xx32 (OR gated IC chip). If you locate a dip or dot (or both even) on one side of the 74xx04 chip that is the "top" where the left-top pin is called pin 1 and the top-right pin is called pin 14. Pin 14 (top-right corner pin) is the POWER PIN. You need to supply the chip with from 4V to 9V of voltage through pin 14.  *Exact same power hook up as 74xx08 and 74xx32


Sadly, because there are 6 gates on the hex (6) NOT gated IC with the same number of pins (14) there is a different layout. It goes as follow. Counting counter-clockwise (anti-clockwise) starting with pin 1 and ending with pin 7 (GND): PIN1=input PIN2=output, PIN3=input PIN4=output, PIN5=input PIN6=output. PIN7 is Ground (GND). 
Do you see the pattern, yet?
 74xx04 only*
- Current pin:  Input 
- Next pin:  Output 
- Then:  Repeat unless the next pin number is divisible by 7 (GND and PWR pins)
Inverter Truth Table
A B
1 0
0 1

THANKS FOR STOPPING BY AT W7R, YOUR DOOR TO TECHNOLOGY. IF YOU ENJOYED THE POST FEEL FREE TO ADD W7R TO YOUR FAVORITES OR FOLLOW W7R. MORE TO COME. -Brian R. H.

AND GATE CHIP (74xx08):

OR GATE CHIP (74xx32):

INVERTER CHIP (74xx04):




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