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Qn on 74LS147 encoder

This is more a question for s.e.b. (x-posted there)

Looking at the datasheet

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then you have: Assuming the 16 pin DIP/SOP style package Low levels on

Input '5' (pin 2) Input ''8' (pin 5) Input ''2' (pin 12)

This is a priority encoder with active low inputs. Therefore, the highest 'value' input, when active, is the encoded value at the output. In this case, that is input ''8'

(See the truth/function table on page 2 of the datasheet)

So the output will be: A = H B = H C = H D = L

(Active low outputs, encoded hex '8', 0111 - invert for active high for clarity = 1000)

Cheers

PeteS

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PeteS
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Best look up the datasheet for the device, then get a new teacher. A teacher who expects you to memorise the pinout and function of an obsolete device is worse than useless.

Paul Burke

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Paul Burke

I encountered the following qn in my test earlier on today.

A 74LS147 encoder has LOW levels on pins 2, 5 and 12, determine the BCD code that appears on the outputs if all the other inputs are HIGH?

+---------+

------O|1 |

------O|2 |

------O|3 |O------- A

------O|4 |

------O|5 |O------- B

------O|6 |

------O|7 |O------- C

------O|8 |

------O|9 |O------- D +---------+

I would appreciate it if someone could tell me how to get the answer as I am confuse as to where pin 12 should be at in the first place.

Thank you in advance.

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