Peripheral Special Function Register Soft-Reset Disable
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Solution Overview
Problem
Conventional microcontroller systems require additional circuitry to maintain peripheral functions during soft resets, leading to interruptions in external circuitry operations, as peripherals like digital-to-analog converters (DACs) are reset along with the microcontroller, disrupting power supply references.
Innovation Solution
Incorporating a control bit in a special function register that allows peripherals to operate in a mode where only a power supply reset resets them, enabling them to maintain functionality during soft resets by selectively excluding soft resets through a multiplexer and flip-flop configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a peripheral is reset along with the microcontroller during a soft reset, then the microcontroller returns to a known state, but the peripheral loses its output voltage settings and external circuitry operations are interrupted
Solution Approach 1:
The reset function is segmented into two independent control paths: one for hard resets (POR, BOR) that always resets the peripheral, and another for soft resets (MCLR, software RESET) that can be selectively enabled or disabled. This is achieved through separate reset signal lines (rst_hard and rst_soft) and a control register bit (SRDIS) that selectively gates the soft reset signal to the peripheral, allowing the peripheral to maintain its state during soft resets while still being reset during hard resets.
2Reliability
If additional circuitry is added to maintain peripheral output during soft resets, then external circuitry can remain functional, but the device complexity and cost increase
Solution Approach 1:
The peripheral device itself is equipped with the capability to maintain its output voltage settings during soft resets through the SRDIS control bit. Instead of requiring external circuitry to maintain the output, the peripheral's internal reset control logic is modified to ignore soft reset signals when SRDIS is set, allowing it to self-maintain its operational state and continue serving external circuitry without interruption.
3Adaptability or versatility
If a control bit is added to selectively enable soft-reset disable function, then peripherals can maintain functionality during soft resets, but the register complexity increases
Solution Approach 1:
The SRDIS control bit provides localized control over the reset behavior of specific peripherals without affecting other devices. Each peripheral that requires soft-reset immunity can independently set its SRDIS bit, creating a customized reset behavior tailored to its specific application requirements. This local quality approach allows different peripherals within the same microcontroller to have different reset characteristics based on their functional needs.
Data Source
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Figure 3
AI summary
A microcontroller has a plurality of peripherals, and at least one control bit, wherein the control bit controls a reset of at least one peripheral such that in a first mode any type of reset resets the at least one peripheral of said plurality of peripherals and in a second mode only a power supply reset resets the at least one peripheral.