Before you start

To get the full experience you need the "Your Own CPU for a Pocket Game" kit, which in turn is a sequel to the "A Watch and a Game from Gates" kit. Lessons 1–3 (memory on a test bench) can be done without them, and in lessons 4–5 your own memory goes into the processor kit's machine.

In the processor kit all the machine's memory is the ram primitive: place it, set its size, and it remembers. It is the machine's last "black box". In this kit we open it up: we build memory ourselves — from the same latches that held the watch digits in the first kit — and put it into the processor in place of ram. The game "Star Harvest" runs on memory built with your own hands.

What we build

• WORD4 — a memory row: a 4-bit word, written at the press of a button, given out on request;
• RAM16x4 — a memory of 16 words: an address decoder, writing into the selected row, reading through OR;
• RAM256x4 — a memory of 256 words (128 bytes) from sixteen RAM16x4: as much as the processor's machine has;
• a two-phase clock — without it, latch memory doesn't work in the processor.

Along the way — one real error, found with the built-in oscilloscope: just like in real life, when everything is built correctly but works incorrectly.

How the kit is organised

• lesson 1 — the cell and the row: a latch plus a "tap" on the output;
• lesson 2 — 16×4 memory: picking one row out of sixteen;
• lesson 3 — 256×4 memory: the same circuit one level up;
• lesson 4 — your own memory in the processor: the game starts and makes mistakes, we look for the cause with the oscilloscope;
• lesson 5 — the two-phase clock: the game runs on your own memory.

What you need. For lessons 1–3 — the first kit's chips (NOT, AND, NOR, SRLatch, DLatch) and the processor kit's (DEC16, OR4). For lessons 4–5 — the whole processor kit machine (GW-CPU, ROM, screen, buttons).

Simulator mode. Lessons 1–2 — in REAL or Fast. From lesson 3 on, a memory of 41 thousand transistors is heavy to compute in REAL: you can build in REAL, but test and play in Fast.