Logic without a chip: reader, writer, memory, compare, math

Not every control needs an IC10. For “vent on when the pressure is too low” a few small logic units on the wall are enough. Each of them does exactly one thing: fetch a value, compare two values, calculate or write a value into a device. Chained together they make a controller.

The four kits#

All logic units come from the Electronics Printer and only need the first printer tier.

Kit	builds, among others
Kit (Logic I/O)	Logic Reader, Logic Writer, Batch Reader, Batch Writer, slot reader, logic mirror
Kit (Logic Processor)	Logic Compare, Logic Math, Logic Select, Logic Min/Max, Math Unary, Logic Gate, PID controller
Kit (Logic Memory)	Logic Memory, hash generator
Kit (Logic Switch)	Lever, Button, Dial, switch, important button

When you build from a kit you choose which part it becomes.

The basic idea: input, output, Setting#

Almost all units mount on the wall in the 0.5 m grid and have three kinds of ports:

• one or two data inputs,
• one data output,
• a separate power port. According to the game data each of these units draws 10 W.

A unit's result is in its Setting. On reader, compare and math units you can only read Setting – the unit fills it itself. Each one can be switched on and off through On, and Error reports a problem.

The exceptions without a power port and with 0 W are the memory, lever, button and dial. They only have data ports.

Fetching and writing values#

The logic reader fetches a value from a device and offers it as Setting. The logic writer does the reverse: it takes the Setting of another logic unit and writes it into a logic type of a device. So it has no readable Setting; next to On it only has ForceWrite (write only).

The batch versions work like lb and sb in IC10: they do not address a single device but all devices of one type on the data network, without looking at names. A batch writer can switch all vents at once, for example.

How to set them up#

Everything happens with the Screwdriver in your hand. Every unit has small setting points; a click jumps to the next choice, with the C key held (default binding) to the previous one. The tooltip shows the current setting.

Unit	Setting points	picks from
Logic reader	device, value	devices on the input network, sorted by name
Logic writer	target, value, source	target on the output network, source (a logic unit) on the input network
Batch reader	device type, value, method	types on the input network; Average, Sum, Minimum, Maximum, Count
Batch writer	device type, value, source	types on the output network, source on the input network

Three rules save a lot of searching:

• The networks matter. A reader only sees what hangs on its input cable; a writer only writes into devices on its output cable. The batch reader also needs a cable on its output, otherwise it reports an error.
• If the target is missing, the old value stays. If the device being read disappears or cannot deliver the value, Error goes to 1 and the reader keeps its last Setting – no NaN, no 0. A chip using lbn gets NaN instead and notices the failure.
• Writers only write on change. If somebody switches the target device by hand, it stays that way until the value at the source changes. A number above 0 in ForceWrite forces another write.

Comparing and calculating#

Unit	modes (Mode)
Logic Compare	0 Equals, 1 Greater, 2 Less, 3 NotEquals
Logic Math	0 Add, 1 Subtract, 2 Multiply, 3 Divide, 4 Mod, 5 Atan2, 6 Pow, 7 Log
Logic Min/Max	0 Greater, 1 Less
Logic Select	0 Equals, 1 Greater, 2 Less, 3 NotEquals
Math Unary	15 functions from Ceil to Not, among them Abs, Round, Sqrt, Sin
Logic Gate	AND, OR, XOR, NAND, NOR, XNOR

Mode is readable and writable – so a chip can switch the operation as well. By the way, the logic gate knows NAND and XNOR, which do not exist as IC10 instructions.

Compare and math units have two data inputs, one per value. With the screwdriver you pick the unit on the first and on the second input network at one setting point each, and the mode at the third. Only logic units with a Setting count as inputs – so you connect a sensor through a reader.

Controls and memory#

• Lever: Open (read and write) is its position, Setting follows it. Lock only blocks the hand; a chip can still flip it.
• Button: a press sets Activate and Setting to 1 for about 0.55 s. Lock locks it.
• Dial: Mode is the upper limit (0 to 1000, in steps of ten with the screwdriver), Setting the position from 0 up to that limit, Ratio = Setting ÷ Mode. A new dial starts with an upper limit of 0 and only turns once you set it.
• Logic memory: holds a number in Setting, readable and writable. By hand you set it with the screwdriver (±100, ±1, with C ±10, ±0.1) or the labeller. It has two data ports and needs no power.

All four have a name and a prefab hash. So a chip can read them with lbn too – a lever on the wall becomes the master switch of a program.

An example: vent by pressure#

Task: an Active Vent should run while the room pressure is below 95 kPa.

1. A logic reader reads Pressure from the Gas Sensor.
2. A logic memory holds the limit 95.
3. A logic compare in mode 2 Less gets reader and memory on its two inputs.
4. A logic writer writes the compare result into On of the vent.

The power draw as a worked example: reader, compare and writer need 10 W each, the memory nothing. That is 30 W – less than the 50 W of an IC Housing. Add 1 W for the sensor and 100 W for the vent.

When the chip is better#

Logic units pay off for single, fixed jobs: show a value, switch a device after one comparison. As soon as you need a hysteresis, several conditions or many devices with the same name, the chain gets long. An IC10 does the same job in one housing.

Here is the vent task as a program, with a band and a lever as master switch:

# Vent by pressure, lever as master switch
define SENSOR -1252983604      # Gas Sensor (StructureGasSensor)
define VENT -1129453144        # Active Vent (StructureActiveVent)
define LEVER 1220484876        # Lever (StructureLogicSwitch)
define NSENSOR HASH("Storage Sensor")  # name of the sensor
define NVENT HASH("Storage Vent")      # name of the vents
define NLEVER HASH("Storage Lever")    # name of the lever
define PMIN 95                 # kPa, switch on below
define PMAX 101                # kPa, switch off above
alias enabled r0
alias pressure r1
alias run r2
alias tmp r3

sbn VENT NVENT Mode 0          # once: mode 0 = blow into the room
start:
yield
lbn enabled LEVER NLEVER Open 0
bnan enabled off               # no lever: off to be safe
beqz enabled off               # lever set to off
lbn pressure SENSOR NSENSOR Pressure 0
bnan pressure off              # no sensor: off
slt tmp pressure PMIN
select run tmp 1 run           # too little pressure: on
sgt tmp pressure PMAX
select run tmp 0 run           # enough pressure: off
sbn VENT NVENT On run
j start

off:
move run 0
sbn VENT NVENT On run
j start

Between 95 and 101 kPa the program keeps the last state – that is the hysteresis the chain above lacks. It writes Mode only once before the loop: every write of Mode resets the active vent's pressure limits to their factory values, even when the mode does not change at all. If the lever or the sensor is missing, lbn returns NaN and the vent goes off. More about this pattern is in IC10: control a device by name and in the lesson hysteresis.

Typical mistakes#

• The unit has no power. Reader, writer, compare and math units need their own power port, not just data.
• Input and output swapped. The port diagram on every device page shows where they are.
• A value does not fit the device. Not every logic type is writable on every device – a sensor's Pressure, for example, is read only. Which values a device knows and whether they are readable (R) or writable (W) is listed on its page under “IC10 and logic”.

Next steps#

• IC10: your first chip – when the chain gets too long
• Displays and consoles: LED displays, consoles, circuit boards – making results visible
• Sensors: gas, daylight, motion, occupancy – where the readings come from
• Academy: levers and buttons, button as a toggle, remembering state