Reverse Engineering PCB Board For Integrated Circuit Placement

Paste the Gate three times so that you have four gates total. Connect the first inputs to net names of IN1 – 4, and the second inputs to ENABLE. Place two more gates –MM74HC02s, which are NOR Gates– to the left of the HC08s. Connect them to the AND Gates as shown on Page.

If you look at the logic gates, you will notice that the AND gates are identical, as are the NOR gates – we are using a single chip for each device, which is obviously not a good idea for Reverse Engineering PCB Board.

To use a single chip for multiple gates, we must go back to the properties window of each device and change the Parts from the default of 1 to 2, 3, and 4 as necessary – 4 gates are in the HC08, and both NOR gates can fit in a HC02. You will notice that the gate designators change from U?A to U?B, U?C, etc. We will now number these designators on the layout drawing extracted from Reverse Engineering PCB Board. This can be done using Tools/Annotate, which will automatically assign numbers to the designators. There are a few options in what parts to number – in this case, use the defaults. You will notice that all the AND Gates are under U1, and the NOR gates are U2.

Now that the schematic diagram is complete, we must make sure there are no errors in the design. Then, we must prepare the design to be imported into the section of Protel that actually creates PCBs. Protel has multiple tools to do both. We are now ready to check our design to make sure there are no errors. This can be done using whats called an Electrical Rule Check (ERC). It can be found under Tools/ERC. There are many thinks the ERC can look for, though for this case, we are mainly concerned about accidental short circuits and the like. Therefore, use the defaults. The ERC should come back reporting no errors.

We are now ready to actually create a PCB from this schematic obtaied from Reverse Engineering PCB Board. There is no information about physical data in a schematic – orientation, spacing, and the like mean nothing. The only data that will be sent to the PCB document besides a list of what nodes are connected to each other (a netlist) are the number of pins on each part, and the Footprint for each part. The latter is where physical data comes into play. A Footprint is a graphical symbol that shows where each pin of a device is physically located. We still must enter this information before we can create the PCB.