As recently as the 1970s, a 4-bit word MCU, for example the Intel 4004, would have handled critical tasks. The 4-bit microcontroller had staying power and found its way into many battery-powered devices. As recently as 2010, specific iterations were still in production, for example, Epson’s S1C060 and S1C63 families.
Modern 4-bit devices are a modern interpretation of an original device that has enhanced architecture, performance, and overall capabilities. The reason for this fortitude is that they are not the same devices that Grandad used or programmed one word at a time.
While 32-bit MCUs are getting all the attention, many embedded systems and products use 8-bit devices. Without risk to the longevity of a new design, selecting a low-pin-count 8-bit MCU that integrates a few precision analogue peripherals, configurable GPIO pins, serial interfaces, and a fast data bus architecture can accomplish a lot.
The same debate that had been occurring around the 4-bit’s successor has the 8-bit device competing against the 16-bit and 32-bit replacements.
8-bit low-pin-count (LPC) microcontrollers have taken advantage of process miniaturisation to improve their features and are now able to perform in more applications than ever before at a lower cost. The core-independent approach by Microchip is an example, where a peripheral can be configured, and then perform a task or tasks in hardware with minimal interaction with the MCU core, thus freeing up processing capability. The innovation seen in 8-bit devices ensures competitiveness against a 32-bit rival.
Hybrid systems are also more prevalent now where an 8-bit device handles delegated tasks requiring fewer resources or at a lower priority.
While even LPC devices were becoming pad-limited by the 0,35 µm technology node, advances in architecture, motor control, smart energy management, Ethernet, and wireless connectivity requirements for home automation and control have led to a new range of applications for 8-bit MCUs.
From the product scope perspective, the reasons why 8-bit devices are just not going away any time soon are the same reasons just over a decade ago that 4-bit devices were still in production from the 1970s.
The following lists shows key performance and device enhancements of where 8-bit devices are continuing to innovate and either retain their established role or enhance it:
• High performance with faster clock speeds
• Integrated features:
o Flash memory.
o Internal high-speed clocks and timers.
o Analogue peripherals.
o Integrated touch controller.
o Motor control.
o Wireless interface.
o Wired network connectivity such as integrated CAN and Ethernet.
• High reliability.
• Small package size.
• Low power consumption.
• Low cost.
• Low electromagnetic interference.
• Wider operating voltage range.
• Code compatibility between older and aging 8-bit devices with new variants or recommended parts.
To change or not to change?
Would one develop a new system using a 4-bit MCU? The answer to this is more than likely an emphatic no. However, could there be a niche opportunity?
Should the application, the budget, or the system requirements meet the need, then one may consider it at the very least. There may also be a deep-pockets client who has a warehouse of them and wants to use them.
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