(Topic ID: 235063)

What is the usage of the LS273 on a CPU board ?


By jimy_speedt

9 months ago



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  • 4 posts
  • 2 Pinsiders participating
  • Latest reply 9 months ago by jimy_speedt
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#1 9 months ago

Hi,

In the context of a coil activation failure, I need to check if the LS273 on the CPU board of a Last Action Hero is ok. I checked all downward components.

Therefore I would appreciate in this context to know what the input, output, clear and clock represent, in simple words if possible

Thank you in advance

#2 9 months ago
Quoted from jimy_speedt:

In the context of a coil activation failure, I need to check if the LS273 on the CPU board of a Last Action Hero is ok. I checked all downward components.

A 74LS273 is an octal D-flip flop. A flip flop is a digital storage element for a single bit. A "D" flip-flop is a sytle of flipflop (there are other kinds ... JK, T ... the letters refer to the overall architecture of the flop ... in most cases these days, we use D flip flops).

The flip-flop will store the signal on the "input" pin when the clock transitions from a low to high signal (this is referred to as a "rising edge"). After a nanosecond or two of delay, the signal that was on the input pin @ the rising edge of the clock will appear at the "output" pin. The "input" pin can change states, but the output will not change unless a rising edge of the clock signal occurs -AND- the input pin is at a stable state before the rising edge of the clock.

The "clear" signal will drive the output low regardless of the state on the input and the rising edge of the clock.

Make sense? Chances are the "output" pin of the flip flop will drive the circuit that enables a solenoid.

#3 9 months ago

Oh, to be clear, "octal" means that there are 8 flipflops in the chip itself. I don't mean to sound condescending saying that ... some people might interpret that as 8 levels of storage .

#4 9 months ago

It is clear, or near to, thanks a lot.

Just one thing. What do you mean by a stable state of the input ?

If we go a bit further than the theory, how can we apply this to the present case ? What should be the input, what is the role of the clock, to get a "1" at the output ? More clearly, why did they put a D flip flop at this place of the circuit ? For this coil 4L (Q43), from which output does the input of the LS273 come ?

Is it only a hardware which ensure the signal is good before passing it further or is there any logic in there ?

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