This data format can be found in bipolar forms. When performing sampling over multiple channels, a multiplexer method using multiplexers switching units or a simultaneous sampling method is used. The multiplexer method performs sampling while switching the multiplexer, meaning that simultaneous conversion of more than one channel is impossible because time is needed to change between channels.
Either type is capable of performing simultaneous conversion over multiple channels. In a system where the analog input channels are switched through a multiplexer method, to perform sampling over multiple channels, the settable sampling period must maintain the following relationship. When using an analog input interface to measure multiple signals, the signals from all measured channels are not necessarily sampled at the same rate.
This means that the sampling period for each channel will increase depending on the number of channels, and a gap will be generated in the sampling rate between channels. Even with multiplexer-based analog input interfaces, time discrepancies can be eliminated by using a simultaneous sampling function extension accessory.
The ATSSA can acquire data at the same sampling rate with no time discrepancy by holding the analog input signals of 16 channels simultaneously according to the control signal from the Analog E series. For sampling clocks that determine sampling cycles, the following main methods are used. A timer element capable of setting the sampling period is installed in the device. As a clock source, this is a method for performing periodic conversions.
Internal clocks are useful for time-series processing at precise and rapid cycles. External clocks can be used for devices equipped with external clock input terminals. Conversion is performed in synchronization with a pulse signal or other signal input from an external source.
This method is useful for synchronizing with external devices. A software clock is a method of performing periodic conversions by synchronizing with the system timer on a PC and sending a start command from the software. However, because errors with VisualBasic's timer control and other functions are large, this method is not suitable for systems requiring fast and accurate cycles.
A trigger is a source for determining the timing at which to start or stop a conversion. Starting and stopping can both be set independently. The main triggers are as follows. Conversion operation starts or stops when the pre-set edge movement rising or falling is input from the external control signal. Conversion is started or stopped according to the signal changes for a specified channel. Buffer memory is where conversion data is temporarily stored.
Such memory not only enables fast and high-performance analog input processing but also significantly reduces the load on the computer. Depending on the application, buffer memory can employ either the FIFO method or the ring method. With the FIFO First In, First Out method, converted data is stored in the buffer memory in a first-come, first-served behavior with data written to the buffer memory first being read first in chronological order.
The converted data read from within the memory is delivered sequentially, with reading of the oldest conversion data remaining in the buffer memory always readable. Data that exceeds the FIFO memory capacity will be discarded and not written, and data that has been read will be discarded from the buffer memory.
The ring method arranges the storage area in the buffer memory like a ring. Conversion data is written sequentially, and when storing beyond the memory capacity, areas where prior conversion data is stored are overwritten. Ring memory is useful when data is not normally obtained but data near a conversion operation stop due to some event should be obtained. With the ring method, once data is captured, it can be read multiple times before it is overwritten.
This intermediate CPU cannot be used for other processes. In the following figure, other processes are only possible after 4 and 5 are finished. During bus mastering, the CPU instructs bus master processing for the device, allowing data to be sent to the main unit's memory directly from the device without going through the CPU. In the following figure, other processes can be performed while 2 and 3 are processing. This function generates priority processing externally by connecting a certain input terminal to an IRQ interrupt request line on the computer.
By detecting changes in external devices, interruption can be used, for example, in applications that perform specific processing and for processing emergency high-priority external commands, to name a few. To operate a device, power is needed, but current consumption indicates how much current that board consumes. This power is usually supplied from the computers expansion bus connector.
This means that the total maximum current consumption of the board should not be more than the rated power capacity of the computer the maximum current that can be supplied to the expansion slot. If the rated power capacity is exceeded, the computer's power supply voltage will be reduced, which could result in such trouble as runaway. For this reason, it's necessary to take appropriate countermeasures, such as extending the computer's slots by using an "expansion unit". Noise can generally be categorized into external or internal noise.
Unlike with electrical testing, various on-site noises can cause unexpected results that do not conform to theory. In such situations, noise will be the driving factor behind any accuracy deviations.
The general rule, particularly when performing measurement, is that noise should not affect the measurement target. To ensure this, it's necessary to take care that impedance, ground levels, and the like, are matching. Oscillators and Frequency Generators 6. Integrated Energy Harvesting Interfaces 7. In-Memory Processing 8.
Data Converters 9. Power Converters Abstract People-to-people P2P technology-assisted interconnections, embedded in a global environment, will be at the core of 21st century communications and will command the technological development of the future.
DOI: Book details. ISBN: Table of contents: 1 Introduction. Revisiting the Frontiers of Analog and Mixed-Signal Integrated Circuits Architectures and Techniques towards the future Internet of Everything IoE Applications Technology-assisted People-to-People P2P interactions, embedded in a global environment, will be at the core of 21st century communications and will command the technological development of the forthcoming future.
As can be seen from Figure 6, as the number of slaves increases, the number of chip select lines from the master increases. This can quickly add to the number of inputs and outputs needed from the master and limit the number of slaves that can be used.
There are different techniques that can be used to increase the number of slaves in regular mode; for example, using a mux to generate a chip select signal. Figure 7. Multislave SPI daisy-chain configuration. In daisy-chain mode, the slaves are configured such that the chip select signal for all slaves is tied together and data propagates from one slave to the next.
In this configuration, all slaves receive the same SPI clock at the same time. The data from the master is directly connected to the first slave and that slave provides data to the next slave and so on. In this method, as data is propagated from one slave to the next, the number of clock cycles required to transmit data is proportional to the slave position in the daisy chain. For example, in Figure 7, in an 8-bit system, 24 clock pulses are required for the data to be available on the 3 rd slave, compared to only eight clock pulses in regular SPI mode.
Figure 8 shows the clock cycles and data propagating through the daisy chain. Daisy-chain mode is not necessarily supported by all SPI devices. Please refer to the product data sheet to confirm if daisy chain is available. Figure 8. Daisy-chain configuration: data propagation. The newest generation of ADI SPI enabled switches offer significant space saving without compromise to the precision switch performance.
This section of the article discusses a case study of how SPI enabled switches or muxes can significantly simplify the system-level design and reduce the number of GPIOs required.
Figure 9 shows the connection between the microcontroller and one ADG Figure 9. Microcontroller GPIO as control signals for the switch. As the number of switches on the board increases, the number of required GPIOs increases significantly. For example, when designing a test instrumentation system and a large number of switches are used to increase the number of channels in the system. Figure In a multislave configuration, the number of GPIOs needed increases tremendously.
One approach to reduce the number of GPIOs is to use a serial-to-parallel converter, as shown in Figure This device outputs parallel signals that can be connected to the switch control inputs and the device can be configured by serial interface SPI. The drawback of this method is an increase in the bill of material by introducing an additional component. Multislave switches using a serial-to-parallel converter.
An alternative method is to use SPI controlled switches. This method provides the benefit of reducing the number of GPIOs required and also eliminates the overhead of additional serial-to-parallel converter.
The switches can be configured in daisy-chain configuration to further optimize the GPIO count. In daisy-chain configuration, irrespective of the number of switches used in the system, only four GPIOs are used from the master microcontroller.
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