user80219: First, please be patient, I'm not electronical person. I am learning Arduino and electronics for hobby and this is my fist time with integrated circuits.

Situation: I'm want to extend the Arduino Nano pins (De/Multiplexer) and keep the state (High/Low) of the new pins until I decide to change it again. For keep the states I think that D-type Flipflop memory-based system can help .
Question 1: On this system can  I change only one bit with a unique signal or need to set all bit states ?
Example (reference image):


Memory, previous state: Q0=0, Q1=1, Q2=1, Q3=0
Arduino: Set pin17 (D2) to High -> Memory: Waiting new data.
Arduino: Set pin16 (D3) to High -> Mux: Pass the value to memory at D0
Memory: Read 1 on D0 (this is my doubt. D1, D2 and D3 don't matter ?)
Arduino: Set pin17 (D2) to LOW -> Memory: Save new data
Memory, new state: Q0=1, Q1=1, Q2=1, Q3=0 ? or Q0=1, Q1=0, Q2=0, Q3=0 ?

Question 2: Are this correct ?
Question 3: Are there a more efficient way to do this?

Notes:

I used a simulator to diagramed the memory based on this datasheet: https://pdf1.alldatasheet.com/datasheet-pdf/view/8337/NSC/74273.html It seems that it is possible, but I want to be sure.
My currently solution is use separated flipflops, but I want to simplify it.
Connections on reference image are simplified.
Sorry about the poor diagram, I don't know programs for beautiful electronical diagrams.
Sorry about typos, not-native English person here.


user80219: Question 1 and Question 2: I was wrong, this is not the correct way. @jsotola and @the_busybee, thanks for the clarification
Question 3: @Nick_Gammon and @Majenko I think you are right, using i2c are more efficient ways to do. But, the @StarCat proposal is more compatible with my current solution. 74hc259 allows me set the state one by one and keep it until I change it again.

80219: <p>First, please be patient, I'm not electronical person. I am learning Arduino and electronics for hobby and this is my fist time with integrated circuits.</p>
<ul>
<li>Situation: I'm want to extend the Arduino Nano pins (De/Multiplexer) and keep the state (High/Low) of the new pins until I decide to change it again. For keep the states I think that D-type Flipflop memory-based system can help .</li>
<li><strong>Question 1</strong>: On this system can  I change only one bit with a unique signal or need to set all bit states ?</li>
<li>Example (reference image):</li>
</ul>
<ol>
<li>Memory, previous state: <code>Q0=0, Q1=1, Q2=1, Q3=0</code></li>
<li>Arduino: <strong>Set pin17</strong> (D2) <strong>to High</strong> -&gt; Memory: Waiting new data.</li>
<li>Arduino: <strong>Set pin16</strong> (D3) <strong>to High</strong> -&gt; Mux: Pass the value to memory at <strong>D0</strong></li>
<li>Memory: <strong>Read 1 on D0</strong> (this is my doubt. D1, D2 and D3 don't matter ?)</li>
<li>Arduino: <strong>Set pin17</strong> (D2) <strong>to LOW</strong> -&gt; Memory: Save new data</li>
<li>Memory, new state: <code>Q0=1, Q1=1, Q2=1, Q3=0</code> ? <em><strong>or</strong></em> <code>Q0=1, Q1=0, Q2=0, Q3=0</code> ?</li>
</ol>
<p><strong>Question 2</strong>: Are this correct ?
<strong>Question 3</strong>: Are there a more efficient way to do this?</p>
<p><a href="https://i.stack.imgur.com/sgd9V.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sgd9V.png" alt="enter image description here" /></a></p>
<p><strong>Notes:</strong></p>
<ul>
<li>I used a simulator to diagramed the memory based on this datasheet: <a href="https://pdf1.alldatasheet.com/datasheet-pdf/view/8337/NSC/74273.html" rel="nofollow noreferrer">https://pdf1.alldatasheet.com/datasheet-pdf/view/8337/NSC/74273.html</a> It seems that it is possible, but I want to be sure.</li>
<li>My currently solution is use separated flipflops, but I want to simplify it.</li>
<li>Connections on reference image are simplified.</li>
<li>Sorry about the poor diagram, I don't know programs for beautiful electronical diagrams.</li>
<li>Sorry about typos, not-native English person here.</li>
</ul>
 80219: <p><strong>Question 1</strong> and <strong>Question 2</strong>: I was wrong, this is not the correct way. <em>@jsotola</em> and <em>@the_busybe</em>e, thanks for the clarification</p>
<p><strong>Question 3</strong>: <em>@Nick_Gammon</em> and <em>@Majenko</em> I think you are right, using i2c are more efficient ways to do. But, the <em>@StarCat</em> proposal is more compatible with my current solution. <strong>74hc259</strong> allows me set the state one by one and keep it until I change it again.</p>
