# Reference designators and bill of materials?

If my schematic has 31 OR gates and 99 AND gates while using CD74HCT32 - High Speed CMOS Logic Quad Two-Input OR Gates

CD74HCT08 - High Speed CMOS Logic Quad 2-Input AND Gates what would my reference designators and bill of materials look like? Below is the schematic:

• This is the sort of thing you might want to consider using a CPLD for, rather than putting 25 14-pin DIP packages on a board like it's 1969. – pjc50 Aug 3 '17 at 10:04
• @pjc50 is it's '69..shouldn't the gates on the right be facing the other way? – Trevor_G Aug 3 '17 at 13:32

Usually when you have a component such as the ones you mentioned, they will have a schematic symbol for each of the four AND / OR gates per component. So for every CD74HCT32, say, there will be 4 OR gate symbols.
Typically they will be referenced by IC1A, IC1B, IC1C, IC1D, for each sub-part of the component. So IC1 is the designator for the whole component as will be found on the PCB layout (if there is one) and Bill of Materials. The suffix letters indicate that it is a sub-part of a whole part so it is easier to see on a schematic.
On the schematic, the sub-part labelled with 'A' will usually be the one that has the part number. and the rest of them will simply be the designator.

So, for 31 OR gates, the schematic will have $\frac{31}{4}$ sets of four designators. So you would have IC1A - IC7C actually connected in the circuit, and for completeness you would show the remaining IC7D on the schematic with the inputs grounded or connected to VCC. The BOM for these devices will simply be IC1 - IC7 are CD74HCT32, and won't show the suffix.

Same again for the 99 AND gates, you would have designators on the schematic from IC8A - IC32C (starting from IC8 to follow on from the OR gates...) and again, IC32D same as above. BOM is the same again. 24 components as the CD74HCT08.

See below - it is easier to determine the function of a circuit this way compared to if you did it like a microcontroller or something.

simulate this circuit – Schematic created using CircuitLab

• so would i just put it on a separate paper like IC1A-IC7C or would I need to include it on the schematic somehow..? – beatsbyse Aug 3 '17 at 9:59
• These are CMOS devices: you never want to leave unused inputs floating. Tie them to ground or Vcc. – DoxyLover Aug 3 '17 at 10:03
• @SeMinPark I don't understand the question. In a schematic editor, you can make a custom component, of which you can create sub-parts, when you go to add the component to the schematic, it will allow you to place the sub-parts one at a time and automatically increment the part number and suffix. – MrPhooky Aug 3 '17 at 10:04
• This is my first digital logic class and I was just wondering how to make a reference designator and bill of materials. Above is the specific example I was given. All these answers seem far too sophisticated for my understanding. – beatsbyse Aug 3 '17 at 10:14
• @SeMinPark Well, when it comes to making the schematic on a schematic designer, it would be able to do it all automatically if it is set up properly. – MrPhooky Aug 3 '17 at 10:15