A little chip design game inspired by KOHCTPYKTOP: Engineer of the People by Zachtronics
# Pharo Chip Designer A little chip design game inspired by [KOHCTPYKTOP: Engineer of the People](http://www.zachtronics.com/kohctpyktop-engineer-of-the-people/) by Zachtronics. It is an inaccurate and highly simplified tool for the design of silicon chip layouts. Unlike common educational tools for logic circuits designs, in Pharo Chip Designer, you need to face the real-life problems like propagation delays or limited amount of layers and available substrate area.  ## How to load The Pharo Chip Designer runs withing Pharo 10.0 environment. Currently, it is not provided as a standalone application because the main purpose of it is not to imitate the original game but to provide a base for own experiments where you want to have full control over the input and output signals. Pharo provides an interactive environment for it. So you first should install Pharo Launcher, then prepare a Pharo 10.0 image and load the Chip Designer into it. 1) Install Pharo Launcher from http://pharo.org/download) 2) Create a new image from the template named "Pharo 10.0 - 64bit (stable)" (32bit can be used too) 3) Run the image, open Playground (Tools - Playground), place the following code there, select it and from the context menu choose "Do it" ```smalltalk Metacello new baseline: 'ChipDesigner'; repository: 'github://pavel-krivanek/PharoChipDesigner/src'; load. ``` In the Pharo welcome window, you can select the prefered theme (light or dark). To run the game, go to top menu bar - _Library - Pharo Chip Designer_ ## Controls | | Normal mode | | ------ | ------ | | LMB | metal | | RMB | N silicon (red) | | Shift + RMB | P silicon (yelow) | | V | next LMB will add a via | | X | delete mode | | S | single step | | R | run simulation | | | Delete mode | | ------ | ------ | | LMB | delete metal | | Shift + LMB | delete silicon | | X | normal mode |  ## Introduction > > The following text is a modified vesion of an article describing the original game that was published on [https://nerdparadise.com/](https://nerdparadise.com) where it is no longer accessible. It can be visited on [archive.org](https://web.archive.org/web/20160404141949/http://nerdparadise.com/tech/electronics/circuits/kohctpyktop/) > When you start the program, you are given a handful of circuit specifications and are expected to create them on the surface provided. You have metal inputs (pads) on the left and metal receivers for outputs on the right. On the top, you have a little toolbar where you can select the input mode of the elements that you can then place the board (substrate). In the tabs below, you can choose between the specification of the circuit and scopes you can run some tests to determine if your circuit works. So back to laying down metal and silicon...  All these materials are capable of carrying current, but only metal can connect to the inputs or outputs...  Metal and silicon can pass over each other on the board without the currents from each interferring unless you add a connector (the little circle thing, 3rd in your toolbox). However, when you try to cross two different colors of silicon, you get something like this...  This is a gate. There are two sorts of gates... ### NPN Gate  Ordinarily silicon will let current travel like metal, but if P (yellow) silicon crosses N (red) silicon, current will only travel through the N (red) silicon if the P (yellow) silicon is also carrying a current. Otherwise, the N (red) silicon will not carry a current across. ### PNP Gate  This is just the opposite. When N silicon crosses P silicon, current will not continue through if the N silicon is carrying a current. Red has to have no current in order for yellow to carry its current across. From these fundamental concepts, traditional logic gates can be constructed. ### AND Gate  Because P silicon will not allow current to travel through N silicon unless the P silicon has current, NPN gates are basically just AND gates. You can chain multiple crossings of P silicon to create a multi-input AND gate...\  ### NOT Gate  The same way an NPN gate is just an AND gate, a PNP gate is just a NOT gate. The P silicon carries current from a constant current source (which +V<sub>CC</sub> provides in the corners of the board). When current from the input is present in the N crossing, then the P silicon will no longer carry a current. ### OR Gate OR is a bit more complicated...\  OR is like a not gate with multiple inputs. The P silicon carries a constant current, but if any of the inputs are active, then the final result will not have current. This is the opposite of the desired output, so adding an extra not gate at the end of this will result in an OR gate. As you can see, even though most logic diagrams show OR as a fundamental unit, when it comes to actual circuits, it is easier to construct a NOR gate.\ ### NOR Gate  If you are feeling lazy, you can make a cheap-n-dirty OR gate by letting all inputs directly touch each other via a piece of metal or silicon...\  This is okay if the inputs aren't being used for any other purpose aside from being fed into this OR gate. When you do this, the current will go BACK into the sources and muck with things if you're using the input signals as inputs anywhere else, so use this design with caution. FAQ --------- **Question:** Does the way how the chip layout is done in the Pharo Chip Designer correspond to the real-life chip design? **Super-short answer:** No **Short answer:** No, it is just an educational game. The real-life chip design is several orders of magnitude more complicated. But the simplifications make it more fun while you still can learn the basic principles and face to some practical problems that many logical simulators do not take into account. **Very long answer:** The voltage is the difference in electric potential between two points. It is crucial to keep in mind that you need two points to measure voltage. If you look at the resistors in series, you will measure potential differences depending on positions of the measuring points. In the electric circuits, you usually use a voltage source like a battery, so the potential difference of its two outputs is the most interesting voltage value for you. Because the voltage needs two points to be measured, some circuit simulators like LTspice forces you to define in the circuit a referencing point, the ground (⏚), although the circuit itself has no real ground connection and is powered only from a battery. I mention this because the relation between the ground and battery outputs may be confusing for novices. An interesting situation occurs when you have an open circuit - like a circuit with a switch in the off state. It may be seen as a circuit where there is a resistor with an infinite resistance or in practice, with a very big value. Then, between the two points, there will be the same potential difference as the voltage source has, independently on the other resistor values (if they are not huge too). Why? If you look at the resistors in series, the voltage divider, the voltage drop of the resistor is directly proportional to its resistance. If you increase the resistance of one of the resistors, the others become proportionally less important. If the resistance value is enormous as in case of open circuit, the voltage drop is practically equal to the potential of the voltage source.  In the digital circuits, we interpret one voltage value as logical 1 and another voltage value as logical 0. For example, it may be 5V and 0V (in reality, some range is accepted, like 0V-0.5V). If you put voltage measuring point before the switch in an open circuit, you will find voltage 5V there - "the logical high". If you turn on the switch, you will close the circuit and produce a short circuit because, in the circuit, we have nothing more than a battery and the switch. The current will not need to overcome almost any resistance so it will grow to significant values and depending on the properties of your current source, it may destroy the circuit components.  For this reason, we need to add some resistor to limit the current. We will add it before the switch itself. Now, when we turn on the switch, we will connect the area before the switch with the ground so the voltage there will immediately drop to zero.  You may ask why we do not put the resistor behind the switch or why we do not measure the voltage before resistor. It is because, in the closed state, every additional resistor close to ground increases the voltage on the switch while we want to keep it as close to zero as possible. Transistors are electronic components that behave like such switch (in digital circuits). The main difference is that we do not control it by hand but by another voltage. The transistor has three pins. The one that controls its state is named "base". When there is no voltage on the base pin, the transistor stays in the closed state that corresponds to the switch that is turned off. When we bring a voltage on the base of the transistor, it will start to behave as a switch in "on