--- To achieve high performance and low cost in a large number of consumer applications, a fully customized analog front end (AFE) combined with a common digital information processor is the only option. In order to meet the conflicting requirements of high-performance analog and low-cost digital control in the same system, today's trend is to use proprietary standard products (ASSP). The advantage of ASSP is to provide high performance analog, low cost digital control and faster time to market with a reusable, low cost system. These ASSPs provide configurable mixed-signal analog functionality as an optimized peripheral module, with the rest of the device sharing reusable modules as many platforms. A flash microcontroller (MCU) is a host that implements shared functions. In addition to digital peripherals such as timers and serial ports, a single ASSP can now integrate high-precision analog-to-digital converters (ADCs), digital-to-analog converters (DACs), operational amplifiers (OA), and supply voltage monitoring. (SVS) and LCD driver. In Figure 1, we show the integrated performance of the mixed-signal flash MCU with the MSP430FG43x.
--- With ASSP-based mixed-signal flash MCUs, design engineers don't have to focus their resources on risky, full-custom hardware implementations to develop flexible, programmable features that can be quickly brought to market.

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Mixed Signal ASSP MCU Solution
--- ASSP is ideal for portable medical devices. A typical device requires a precision sensor interface circuit, communication functions, real-time clock function, non-volatile memory for patient data, long battery life, and the flexibility to program the flash MCU in the application. Figure 2 shows the block diagram of a single-chip glucose meter.
--- A biocatalyst test piece was used to measure the glucose content of a small sample of blood. When a blood sample is applied to the test piece, a small current of the μA (microampere) level is generated and is proportional to glucose. A bias voltage is then supplied to the test strip by a 12-bit DAC inside the flash MCU. We use a transimpedance amplifier implemented with an operational amplifier with an integrated flash MCU to convert the current produced by the biocatalyst into a voltage. We use a programmable feedback resistor array to adjust the output of the op amp to a range that can be measured by an embedded 12-bit ADC that can be internally provided by the flash MCU, eliminating the need for external components.
--- Biocatalysts are sensitive to temperature, making this situation even more complicated by the fact that the measurement cycle can last up to 30 seconds. For example, the measurement cycle may start from a warm environment such as in a user's room, and the conversion result is completed in an outdoor environment in a cold winter. To do this, we use the internal temperature to measure the temperature at the beginning and end of the measurement cycle. If the temperature difference between the two is too large, the reading will be discarded and the user will be alerted.
--- The patient's measurement data will usually be recorded and transmitted for analysis by the user or physician. Since the flash MCU memory is in-system programmable (ISP), a portion of the flash is directly allocated for data logging. With a portion of the MCU memory for recording, no external data memory is required. Modern embedded flash erasable and reprogramming programs up to 100,000 times, higher than the working life of the instrument.

Power Monitoring (Power Aware) application
--- To extend the working life, engineers must recognize power issues when designing battery-powered instruments. The normal operating mode must be a power-saving, low-power standby mode. In order to save power, the entire system must be analyzed to run only the required tasks. Unnecessary tasks waste power and should be completely removed. Unused peripheral modules must be disabled. With ASSP, all peripheral modules are embedded in the flash MCU and are fully software controlled for easy operation. The disable circuit is simplified to software operation by simply setting the bit in the peripheral control register.
--- In addition to the lowest power consumption, on-demand performance and fast switching between operating states are usually required. The timing of the system must be flexible enough to meet the following conflicting needs:
--- ● Stability required for precise time base
--- ● Low power consumption required to extend battery life
--- ● Speed ​​required for high performance
--- ● Sensitivity to rapid response to events
--- The best clock solution is a combination of two timing methods: one is to use an external 32kHz surface crystal as the auxiliary clock (ACLK) for low power consumption and stability; the other is to use fast start, high speed The on-chip numerically controlled oscillator (DCO) acts as the system's master clock (MCLK). ACLK is always on and only counts one LCD driver and one timer for real-time interrupts. High-speed MCLK clocks the CPU and high-speed peripherals to enhance processing power and ability to react quickly to events. The DCO is a low Q, RC type oscillator that is close to "zero delay" and can be started in less than 6μs.
--- In order to achieve a stable output of the DCO clock, which does not change with temperature and voltage, we use a frequency-locked loop (FLL). The FLL is a continuous frequency integrator that always adjusts the DCO frequency to a stable reference ACLK fraction in the background. The adjusted DCO is compared to ACLK and fed back to an up/down counter that automatically increases or decreases the output of the DCO to match the frequency of the DCO to the frequency of the ACLK. This has the same effect as increasing the DCO frequency to the ACLK frequency. Figure 3 shows the DCO/FLL combination.
--- The combination of DCO/FLL outlines the power monitoring ultra-low power activity profile, which extends usage time in power-saving standby mode without compromising performance. When an event-driven interrupt requires system services, the DCO is automatically enabled and the CPU is activated. The high-speed DCO clock system will meet the demand as quickly as possible and then return to standby.
--- Always open ACLK clock timer provides convenient embedded real-time timing. Timed with a 32 kHz surface crystal, the timer separates the sources by 2^15, which triggers an interrupt every second. Because the DCO startup time is not clocked for the CPU and software at this time, the embedded real-time timing function can be implemented as a simple interrupt with no impact on overall performance. The CPU time required for the basic real-time timing function should be less than 100. If the CPU is clocked at a nominal 1MHz frequency, the real-time timing function operates at 100μs per second (ie, 0.0001). If the CPU current is 250μA, the real-time timing function increases the overall system power budget by less than 25nA.

Mixed signal flexibility
--- The performance of mixed-signal flash MCUs in terms of integration is impressive, but few applications sacrifice integration to achieve analog performance and design flexibility. A product with a wide range of applications can achieve a higher return on investment, which is ideal from the perspective of the chip manufacturer. To address the issue of flexibility, the Mixed-Signal Flash MCU provides built-in software-simulated peripherals for fixed functions with built-in programmability.
--- Embedded ADC provides complete control of input channels, sampling time, sample rate, and voltage reference. Use the software to select the specific features you need. The DAC provides the ability to select the output format, trigger source, multiple DAC groupings, and the ability to configure the analog output buffer for optimal power and drive balancing. OA is typically one of the most special and critical analog components of any design. It has several registers that implement full programmability including setup time, rail-to-rail inputs, and feedback resistors. Complex circuits such as differential amplifiers and instrumentation amplifiers can be easily implemented with multiple embedded OAs.
--- With the flash-based MCU-based ASSP, software can be configured for all analog and digital peripheral modules, which can continue to enhance the application until the final product is shipped. Not only does this not cause a long ASIC delivery cycle, but it also does not cost the redesign. In addition, with a flash-based configuration, the same hardware can be reused for several end products. For example, a product may be offered to several different regions that require different user interfaces. With flash memory, you can embed a specific zone configuration. Flash-based products also offer field upgrades that can be programmed in the future.

Better performance
--- Embedding mixed-signal peripheral features directly into the flash-based MCU-based ASSP eliminates the overhead required to separate the interfaces between external devices, thereby improving system performance. For example, the shared interface between the external data converter and the MCU is a synchronous peripheral interface (SPI) bus. The SPI takes at least board space and requires an MCU serial port with four signal pins: chip select, clock, data input, data output. The higher cost lies in the software overhead of servicing the SPI Interrupt Service Routine, typically within the interrupt overhead and storing the 50 system CPU cycles required to receive and send data. At 100ksps ADC sampling rate and software cost of 50 cycles per sample, the MCU must retain 5 million cycles or MIPS. With embedded data converters, software services are as simple as reading a single register and then transferring the results to memory, reducing system cycles by 50% and power consumption by more than 50%.
--- To further improve performance while reducing power consumption, new ASSPs such as the MSP430FG43x include direct memory access (DMA) controllers. DMA provides the ultimate glue between embedded mixed-signal peripherals for fully configurable, automated, CPU-free data transfer. The use of peripherals such as data converters can significantly enhance the performance of DMA, which can move data in and out of the storage table. With DMA, only two system cycles are required per transfer, reducing system overhead by a factor of 25 compared to systems connected to external devices. With DMA, new available system resources can be reassigned to more advanced subdivisions, or used to achieve significantly longer standby intervals, reducing the power required to extend battery life.

to sum up
--- Today, developing ASSPs based on mixed-signal flash MCUs that can be quickly brought to market, tightly packed, and more accurate simulations requires a new way of thinking. The state-of-the-art MCU-style in-circuit simulator (ICE) was replaced by embedded analog. The small embedded analog logic core resides on the actual ASSP itself and is accessible through the industry standard JTAG interface. Embedded analogs are becoming increasingly important for high-performance mixed-signal systems that must maintain the integrity of the microvolt analog signal. The cumbersome ICE is almost impossible to achieve high-precision signal integrity, it is very sensitive to wired interference.
--- With embedded simulation technology, from the beginning of development, hardware engineers can concentrate on developing actual production systems and debugging. Combining the superior flexibility of ISP flash memory with common embedded emulation enables the design to enable true system-level development of today's mixed-signal ASSPs, reducing costs and further simplifying development and speeding development process.