Microchip Claims New MCUs Raise the Bar on Enhanced Code Security

November 28, 2023 by Arjun Nijhawan

Microchip has announced a new family of MCUs to increase security and reduce board complexity and cost for monitoring and telemetry applications.

Microchip has announced a new family of microcontrollers (MCUs), the PIC18-Q24, equipped with new features for enhanced security, lower cost, and increased flexibility. With these new devices, Microchip aims to boost the security of its MCUs and processors to meet the market demand for more secure embedded systems. 



The new PIC18-Q24 family is designed to secure embedded designs.

A RISC Architecture With Standard MCU Features 

The datasheet for the PIC18-Q24 family indicates that the lineup is available in 28/40/44/48-pin configurations, with package types ranging from SOIC to VQFN. The higher pin count devices in the family have more flash memory, data SRAM, and additional analog-to-digital converter (ADC) channels. 


PIC18-Q24 family

Higher pin count devices in the PIC18-Q24 family have more memory and ADC channels. 

Microcontrollers in the lineup use a PIC18 CPU. The CPU uses a modified Harvard architecture (as opposed to a Von Neumann architecture), with separate buses for instruction and data. The PIC18-Q24 MCU lineup has up to 64 KB of program memory to store execution instructions, 4 KB of data memory (volatile SRAM), and 512 bytes of data EEPROM (non-volatile ROM). 


Block diagram of the PIC18-Q24.

Block diagram of the PIC18-Q24.


One interesting standout from the block diagram is the program, debug, and supervisory modules, which contain a sub-block called “enhanced code protection.”


Enhanced Code Protection Heightens System Security

Microchip claims that enhanced code protection prevents malicious actors from programming, reading, or modifying code on the PIC18-Q24.

The PIC18-Q24 contains various registers called configuration registers. A configuration register controls the stack overflow/underflow reset enable feature (Bit 4 of CONFIG4 register). If a stack overflow or underflow occurs when this bit is set, the device will reset. With enhanced code protection, additional configuration bits allow the user to "write protect" certain blocks of the microcontroller.

Write protection inhibits unwanted or unauthorized programming or modification of memory and instructions. For instance, Bit 0 of the CONFIG12 register is ICSPDIS, an active low bit that fully disables the programming and debugging interface. This bit is intended for use in production systems with contents that should never be erased or even modified once deployed to the field. Once this bit is set, the device can essentially never be reprogrammed again, even using a bulk erase operation first.

Bit 0 of CONFIG12 controls the programming and debugging interface

Bit 0 of CONFIG12 controls the programming and debugging interface. 


According to the press release, such protection is critical for IoT devices such as thermostats and home appliances that are connected to the cloud. Using the cloud, it would be possible for malicious actors to modify and control devices that use microcontrollers. With features such as PDID, the device becomes inaccessible to such attacks. 


Multi-Voltage I/O Feature Boosts Adaptability, Cuts Cost

The PIC18-Q24 lineup is also equipped with multi-voltage I/O (MVIO) to handle various sensors and peripherals that operate in different voltage domains.

Consider a typical modern PCB: some components may operate at 3.3 V, 5 V, or even 1.8 V. Level shifters are typically used to translate from one voltage domain to another. However, with MVIO, external level shifters are not required to translate digital logic levels.

While the datasheet indicates that MVIO does not work for analog inputs, MVIO allows pins to operate on a digital voltage domain separate from the main voltage domain, VDD. This domain, called VDDIOx, is connected to internal voltage monitoring and power-on-reset (POR) circuitry, which arms itself when the voltage drops too low and switches off when the voltage reaches the desired high level. In fact, the user can monitor the behavior of the POR circuit using register PCON1, Bit 3. 


PCON1 Bit 3 allows for monitoring of VDDIO POR.

PCON1 Bit 3 allows for monitoring of VDDIO POR.


This is the PORVDDIO2 bit, which indicates that a power-on-reset occurred due to an event on VDDIO. In this way, there is no need for a level shifter on the final PCB, which reduces overall system cost and allows more space on the PCB for other components.


Available Support Tools 

Microchip supports the new MCUs with development tools that integrate with the company's MPLAB Code Configurator (MCC). These tools include the PIC18F56Q24 Curiosity Nano Evaluation Kit (EV01E86A), which provides direction when designing with the PIC18-Q24 family and may reduce the time to market. 



All images used courtesy of Microchip.