1
\$\begingroup\$

I just made something cool (or at least in my mind it is), and I wish to save it under the form of a schematic. So I started making one with CircuitLab.

The circuit includes a shift register chip (74HC595N), which I couldn't find on CircuitLab. Is there any specific drawing to represent a shift register on a schematic ?

\$\endgroup\$
2
  • \$\begingroup\$ Is it 74HC959 or 74HC595? \$\endgroup\$
    – AndrejaKo
    Apr 26 '13 at 23:39
  • 1
    \$\begingroup\$ I can't help you with circuitlab, but if you just want a schematic picture, you can take a look at the pages number 3 and 4 of the datasheet for that part. Linked datasheet if for NXP's part, but the part itself is generic and made by a number of different manufacturers which usually have same almost completely same datasheets. \$\endgroup\$
    – AndrejaKo
    Apr 26 '13 at 23:42
3
\$\begingroup\$

For simulation puropses, XMPPWocky's answer is good - you need to either make it from components available in CircuitLab or if you were using SPICE you would probably use a macro model (or possibly subcircuit) to describe the behaviour.

However, if you are wanting to draw a proper schematic and possibly produce a PCB, then getting hold of a proper EDA package to produce the schematic, board layout, gerber files, BOM, etc is a good idea. Some EDA packages incorporate simulation also.
In software of this type you would typically either download the manufacturers symbol and footprint for the component, or if they are not available in your format, you would create them youself. They may already be present in the library of you package, some have very extensive component libraries.

In an typical schematic, the symbol would look something like this:

74HC595

The PCB footprint might be like this:

74HC595 footprint

And some packages have a 3d view which will look something like this:

74HC595 3D

There are many good EDA packages out there, ranging from expensive (e.g. Altium) to more affordable (Diptrace, Eagle) to free (Kicad, GEDA) For a very good free option which is quite useable for professional purposes, Kicad is well worth trying out (the above images are from Kicad).
Like any complex design tool, it has a steep learning curve, but it's well worth the time if you intend to catalog and produce your designs in the future.

\$\endgroup\$
2
\$\begingroup\$

You could do this in two ways:

  1. Model it using the Custom Part model. However, this would not actually act like a shift register; it would prevent you from getting useful results out of simulation. However, it is more compact than the second option.

  2. Model it as a chain of flip-flops (which it actually is, internally). This would make simulation possible. However, it would use a lot of space on the schematic.

Like this:

schematic

simulate this circuit – Schematic created using CircuitLab

\$\endgroup\$
1
\$\begingroup\$

schematic

simulate this circuit – Schematic created using CircuitLab

CircuitLab does not support it, so the schematic above is useless in this context. But the drawing above is typical for programs that can support buses, bundles and arrays. Provided as a reference for future searches, nomenclature will vary according to tool used.

To translate: it says that REG1 has In on the D input and Q1 on the Q output. Reg2 has Q1 on the D input and Q2 on the Q output. etc. etc. until the end where Reg8 has Q7 on the D input and Out on the Q output.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.