i8048 Microcontroller
The Intel 8048 (part of the MCS-48 family) was a fundamental component in 1980s computing, primarily used by Amstrad in its PC-compatible (XT) lines and the PCW series to manage the keyboard.
Unlike Amstrad CPC computers (where the keyboard is a passive matrix scanned directly by the AY-3-8912 sound chip), models with external or “intelligent” keyboards delegated this task to the i8048.
The i8048 in Amstrad Equipment
- Amstrad PC1512/PC1640: EThese computers used an Intel 8048 (with Amstrad part number 40042) inside the keyboard. Its function was to scan the key matrix and send scan codes serially to the computer using Amstrad's proprietary protocol, which was incompatible with the IBM standard of the time.
- Amstrad PCW 8256/8512: In this series, the keyboard microcontroller did not just send the pressed key; instead, it repeatedly transmitted the complete state of the matrix (17 words of 12 bits) to the central system.
- Evolution (8049): In later models of the XT range (such as the PPC512 or the PC2000 series), Amstrad replaced the 8048 with the 8049, which offered double the memory to handle more complex scan codes and additional functions like keyboard lock.
i8048 Technical Specifications
This chip was Intel's first successful microcontroller (released in 1976) and combined all the elements of a computer into a single piece of silicon:
- CPU: 8-bit processor.
- Memory: Included 1 KB of internal ROM (where the scanning program resided) and 64 bytes of RAM for temporary data.
- I/O: Featured 27 input/output lines, ideal for monitoring a large keyboard matrix.
- Architecture: Used a modified Harvard architecture, strictly separating program memory from data memory.
Why was it important?
In external keyboards, the i8048 enabled serial communication, which drastically reduced the number of wires required in the connector (usually only 4 or 6 wires) instead of having to run every row and column of the matrix to the motherboard. Additionally, it allowed the keyboard to independently manage functions such as auto-repeat and LED control.
Documentation
You can view the PDF documentation regarding the chip at the following link: