The **GMC-4 (Gakken Micro Computer 4)** is a 4-bit educational computer kit originally released by Gakken. The "R" usually refers to the modern reproduction or revised versions. It is designed to teach the fundamentals of machine language and CPU architecture. --- ## 1. Core Electronic Components The GMC-4 is a simple system-on-a-chip (SoC) style architecture. Below are the primary hardware components: | Component | Description | | :--- | :--- | | **Microcontroller (MCU)** | Typically an **Elan EM78P447** (or similar 8-bit MCU) programmed to emulate a 4-bit CPU architecture. | | **LED Display** | A single-digit **7-Segment LED** display used to show memory addresses and data (0-F). | | **Indicator LEDs** | A row of **7 binary LEDs** used for output and status indicators. | | **Input Interface** | A **20-key numeric keypad** (0-F plus function keys like RESET, RUN, ADR SET, INCR). | | **Sound Output** | A small **Piezoelectric speaker** used for simple beeps and programmed musical notes. | --- ## 2. Technical Specifications Despite being an 8-bit chip physically, the logical architecture mimics classic 4-bit systems from the 1970s. * **Architecture:** 4-bit (Data bus). * **Memory (RAM):** 80 nibbles (40 bytes). * *Program area:* 00 to 4F (80 steps). * **Registers:** * **A:** Accumulator (4-bit). * **Y, Z:** Index registers (4-bit). * **A', Y', Z':** Backup/Flag registers. * **Clock Speed:** Low frequency (simulated), roughly in the kHz range to allow users to follow operations. --- ## 3. Programming Logic The electronic logic follows a strict **Opcode + Operand** format. Programs are entered in Hexadecimal. ### Sample Opcode Structure ```assembly F 1 ; Opcode F (Sound), Operand 1 (Pitch) 1 5 ; Opcode 1 (Load A), Operand 5 (Value) ``` --- ## 4. Power Circuitry The device is highly efficient and designed for portability: * **Voltage:** 4.5V (typically powered by 3x AA batteries). * **Regulation:** Basic capacitor-based smoothing; the MCU operates directly on the battery voltage range.