What is meant by data transfer interface? What do you mean by interface?
Interfaces are a device that allows data exchange between a source and a receiver.
Parallel interface.
It is an n-bit bus through which data is input or output in parallel along communication lines, each of which has its own weight. Data is exchanged between the source and receiver via the n-bit bus.
Let's say data is entered into the host from an ADC, then the ADC is the source, the host is the receiver. The CS signal is selected when the address on the HA of the installed process coincides with the address assigned to the port or device with which data is being exchanged. Devices whose addresses do not match the address of devices on the ShA are in a neutral state (“resting”). The data is installed on the SD simultaneously.
The data is labeled by category. Each digit can contain either 0 or 1. The digit number corresponds to its weight. When combining 4 digits into 1 character, we get a low and high digit. In order to write a number into a digit, you need to add the value of the highest and lowest digits.
The parallel interface includes: internal buses (addresses, data), a printer interface, for connecting external devices such as ISA, PCI, AGP, LPT.
Dignity: high speed of information transfer.
Flaw: Limited communication line length, exposure to external interference, information transfer speed limited by the internal bus.
Parallel interfaces are used to exchange data inside the PC and an external device located on a short distance(LPT ~ 3m).
If the speed of data exchange between the processor and an external device does not match the speed at which the processor operates, buffering is used.
A buffer is a memory that can exchange data at a speed that matches the speed of the external device (buffer fill) and subsequently exchange data between the buffer and the processor at processor speed.
Example of buffers: Cache memory, buffer memory as part of data input/output devices (ADC boards, video cards).
Serial interface.
Data is transmitted serially over one wire. Serial interfaces include: COM port, USB, PC/2 (mouse, keyboard). Only two devices can be connected.
Serial synchronous interfaces (SSI) – for data transmission, in addition to the data line, clock pulse (signal) lines are used.
Reading and writing of data is performed on the edge of the clock pulse (-data exchange synchronization pulse).
If more than one device is connected to the data line, then the selection of the device with which data is exchanged is carried out by a special CS signal.
These interfaces include: SPI, I 2 C
These interfaces are used to exchange data within a computer containing a microcontroller and some peripherals (ADC, DAC, temperature sensor) inside the device.
Serial Asynchronous Interface (SAN)
PAN contains no synchronization signals (no CLK (clock signals)). Data exchange is carried out by sequentially installing data bits on the data line at equal time intervals.
● Serial asynchronous half-duplex interfaces
RxD – receiver,
TxD – transmitter.
The state of the same discharge is transmitted at regular intervals. IN this type interfaces, only 2 devices (receiver and transmitter) can participate in data transmission.
1 – start pulse (synchronizes the transmission process);
2 – a data byte is transmitted (the number of transmitted bits is 5-8);
3 – service information is transmitted (parity check bit);
4 – stop bits (minimum 2) – separating bits between sequentially transmitted messages.
3+4 – service bits
The parity check bit is used to eliminate random errors (the value of the bit is 1 or 0 in the information clock, the value is set so that the total number of ones is even).
If there are three ones in the byte, then the parity bit = 1, if 6, then the parity bit = 0.
Stop bits determine the minimum time interval between adjacent messages. There can be 1 or 2 of them depending on the adopted data exchange protocol. If data is sent over a time interval greater than the stop bit interval, then this does not lead to a failure in data transmission over the interface; if it is less, it does.
Data transfer speed is measured in [baud]. (1 baud = 1 bit/s).
Advantages:
Minimum wires are required for data transfer,
Works well over long distances.
The implementation of the interface itself is simpler.
Flaw:
Because data flows serially, the length of the communication line can be up to hundreds of meters;
The data transfer rate is lower than that of the parallel interface (this problem can be solved by using clock cycles)
Used in the first telegraph relay lines.
● Serial asynchronous duplex interfaces
Duplex mode – information is transmitted in both directions at the same time. The source and destination have different priorities.
Industrial interface RS-485 (Duplex mode)
This interface allows you to connect several devices in one SD.
Master – means that the computer is the first to send a request via the RS-485 communication line, containing the address of the device with which it will exchange data. All devices accept this request while in standby mode, and the device whose address matches the number specified by the PC receives or transmits data in accordance with the established data exchange protocol.
As a rule, all devices are actuators.
RS-422 (Half duplex mode)
tcom > tup
tcom – sending time between commands
tп – time of data transmission of any of the devices (duration of the response of the nth device to eliminate competition of signals along the data line).
Specialized converters are used to convert signals. Signal conversion devices for RS-422 and RS-485 interfaces incorporate galvanic isolation. Data transmission via RS-422, RS-485 interface lines is carried out over 2 wires using a differential communication line to reduce the influence of external wires.
| Data+ Data- | Rs-485 |
| TxD+ TxD- RxD+ RxD- | RS-422 |
The communication line length can reach up to 1 km using a standard conversion device.
Types of I/O Devices
1. Devices installed on the computer bus (PSI, ISA). They communicate directly with the internal bus and can enter information fairly quickly.
2. External devices (COM – port, LPT – port, USB – port). The output device converts the digital code into voltage. Digital (discrete) information output cards are used to control equipment using the “on/off” principle.
Modern signal input-output boards can include a Digital Signal Processor (DSP - digital signal processor). It performs the function of pre-processing input signals.
Can multiplex data supplied to the ADC; digital data filtering (removal of interference), frequency analysis of the signal (constructed using Fourier transforms).
I/O Device Specifications
Characteristics for ADC:
Number of digits;
Maximum input voltage (There are a number of standard maximum voltages: 1; 2.5; 5; 10 V);
Polarity (unipolar: U=0÷Umax, bipolar: U=-Umax÷Umax);
The presence of a multiplexer (designed to switch channels and determine from which channel the signal will go to the ADC)
If there is a multiplexer, a parameter appears such as the conversion frequency of the ADC channel. The ADC passport indicates the total conversion frequency. Therefore, if f p- conversion frequency specified in the passport, then the frequency of conversion of one channel: f channel=fp/m, Where m– number of channels.
The presence of galvanic isolation (used to separate the zero potentials of the operation of computing and external devices);
Volume buffer memory(for high frequency systems).
When recording, information is lost because The write speed is less than the read speed.
Many ADCs have the ability to connect a differential signal.
Data interfaces are evolving so quickly that it is difficult for storage system manufacturers to keep up. Every year, interfaces appear that make it possible to achieve data transfer speeds many times higher than existing devices. Switches and network adapters begin to support the latest high-speed interfaces long before they become available in storage systems.
The table below shows the development of throughput capacities of storage connection interfaces on a timeline.
Interface development trends
Below are expected years of new data rates for various interfaces, based on industry research. History shows that for many interfaces the development cycle for new standards is 3-4 years.
It is worth noting that from the moment the specification of a new interface is approved until the products that support it appear on the market, several months usually pass. Widespread adoption of the new standard may take several years.
Work is also currently underway to develop versions of existing interfaces with reduced power consumption.
Fiber Channel
32Gbps FC (32GFC)
Work on the 32GFC standard, FC-PI-6, began in early 2010. In December 2013, the Fiber Channel Industry Association (FCIA) announced the completion of the specification. Products supporting this interface are expected to hit the market in 2015 or 2016. 32GFC will use a 25/28G SFP+ connector.
The 128Gb FC multi-channel interface, known as 128FCp (quad-channel parallel), builds on 32Gb FC technology and has been added to the official FC roadmap. The T11 Committee gave the project the name FC-PI-6P. Specification completion is planned for late 2014/early 2015, with products becoming available in 2015 or 2016. The 128GFCp will likely use QSFP+ connectors, with support for CFP2 or CFP4 connectors also possible.
Some manufacturers market 32GFC and 128GFC as "Gen 6" Fiber Channel because this version supports 2 different data rates in two different configurations (serial and parallel).
64Gbps FC (64GFC), 256Gbps FC (256GFC)
Development of the 64GFC and 256GFC standards began in the FC-PI-7 project. Technical stability is expected in 2017. Each FC revision is backwards compatible with at least two previous generations.
FC as SAN interface
Apparently, Fiber Channel will remain the dominant technology for building SANs for the foreseeable future. Significant amounts of money (billions of US dollars) have been invested in FC infrastructure over the years, primarily in data centers that will remain operational for many years to come.
FC as a disk interface
Fiber Channel as an interface for connecting drives is becoming a thing of the past as enterprise drive manufacturers move to 6Gbps SAS and 12Gbps SAS. Due to the relatively large volume of 3.5-inch FC drives being released in enterprise disk subsystems, it is expected that FC will continue to be used to support them for some time. Among 2.5-inch drives, Fiber Channel is likely to be available on very few devices.
Fiber Channel over Ethernet
FCoE (FC-BB-6)
The FC-BB-6 standard was completed by T11 in August 2014. FC-BB-6 standardizes the VN2VB architecture and improves Domain_ID scalability.
VN2VN is a way to directly connect FCoE end nodes (Virtual N_Ports) without the need for FC or FCoE switches (FC Forwarders), allowing for simplified configuration in small locations. This idea is sometimes called "Ethernet Only" FCoE. Such networks do not require zoning, resulting in less complexity and lower costs.
Domain_ID Scalability allows FCoE fabrics to scale to larger SANs.
40Gbps and 100Gbps
40Gbps FCoE is still a year or two away. Perhaps the interface will appear simultaneously with 32Gb FC. The IEEE 802.3ba 40Gbps and 100Gbps Ethernet standards were ratified in June 2010. New products should be available over time.
It is likely that 40Gbps and 100Gbps FCoE, based on 2010 Ethernet standards, will be used initially for ISL cores, thereby leaving 10Gbps FCoE primarily for end connections. It is expected that future versions of 100GFCoE cables and connectors will be available in 10x10 and then 4x25 configurations.
InfiniBand
Currently, products using 100Gbps Infiniband EDR (Enhanced Data Rate) are already commercially available. EDR uses 25/28G SFP+ connectors, as well as Ethernet and Fiber Channel interfaces.
InfiniBand High Data Rate (HDR), supporting 2x the speed of EDR, is expected in 2017 or 2018. HDR host adapters may require PCIe 4.0 slots.
Ethernet
In July 2014, 2 different industry groups—the 20G/50G Ethernet Consortium and the IEEE 802.3 25Gb/s Ethernet Study Group—announced the start of new job over the Ethernet specification to take advantage of the 25Gb PHY in a single-lane configuration. The result was a single-band connection specification similar to existing 10GbE technology, but 2.5 times faster. Products using these technologies are already available. There are also plans to develop a 50GbE standard using 2 25GbE lanes. The specification is planned to be completed in 2018-2020.
2.5GbE and 5GbE standards are in development, which allow increasing network throughput without additional costs using Category 5e cables. The NBASE-T Alliance has released version 1.1 of the NBASE-T specification, which describes the physical layer implementation. The Technical Working Group is working on the specification for the PHY-MAC system interface, magnetic and channel characteristics. In addition, employees from 25 companies are involved in the development of IEEE 802.3bz 2.5/5GBASE-T standards. Products supporting 2.5GbE and 5GbE are already appearing on the market.
SAS
12Gbps SAS
The SAS 3 specification, which includes 12Gbps SAS, was submitted to INCITS in Q4 2013. 12Gbps SAS products for end users began appearing in the second half of 2013, including SSDs, network adapters (SAS HBAs) and RAID controllers. 12Gbps SAS allows you to take full advantage of the PCIe 3.0 bus.
24Gbps SAS
The 24Gbps SAS interface specification is currently under development. It is predicted that the first components using 24Gbps SAS may appear in 2016 or 2017, with the first products available to users in 2018. 24Gbps SAS is being developed to be fully compatible with 12Gbps and 6Gbps SAS. A different encoding scheme may be used.
Prototypes for the 24Gbps SAS interface will use PCIe 3.x technology, but it is likely that final products will use PCIe 4.x technology.
SCSI Express
SCSI Express implements the well-known SCSI protocol over an interface PCI Express, reducing latency by using PCIe. It is designed to match the improved speed SSD drives. SCSI Express uses the SCSI over PCIe (SOP) and PCIe Queuing Interface (PQI) protocols, creating the SOP-PQI protocol. The controllers connect to devices using the SFF-8639 connector, which supports multiple protocols and interfaces such as PCIe, SAS and SATA. SCSI Express supports PCIe devices using up to 4 lanes.
SCSI Express was first proposed in 2011 and accepted as a formal project in 2012, but was not developed until 2015. It is not yet known when the first SCSI Express products will be released to market.
SAS connectivity options
New SAS connectivity allows data to be transferred over long distances using active copper patch cords and fiber optic cables. The Mini SAS HD connector (SFF-8644) can be used for 6Gbps SAS and 12Gbps SAS.
Future features include support for Zoned Block Commands (ZBC) and Shingled Magnetic Recording (SMR) for high-capacity discs.
SATA Express
The SATA Express specification is included in SATA version 3.2. SATA Express allows SATA and PCIe client solutions to coexist. SATA Express allows for increased transfer speeds of up to 2 PCIe lanes (2GBps for PCIe 3.0 and 1GBps for PCIe 2.0) compared to current SATA technology (0.6GBps). This speed is suitable for SSDs and SSHDs, while regular HDDs can continue to use the existing SATA interface. Each device can use a PCIe or SATA connector, but not both at the same time. The individual signal generated by the device tells the host whether it is a SATA or PCI Express device. As of mid-2015, SATA Express is supported by a very small number of motherboards. It is not yet clear whether SATA Express will be accepted by the market, and we should not expect a large number of products to appear in the near future.
New SATA Features
New features planned for the future include enterprise-grade options such as remote power shutdown, improved array recovery, and optimizations for NAND flash devices. It is also planned to support SMR (Shingled Magnetic Recording) technology.
Thunderbolt
Thunderbolt 2 was introduced at the end of 2013, and many devices using this interface are now being produced. Thunderbolt 2 data transfer speed is 20 Gbps.
Thunderbolt 3 (40 Gbps) was announced in June 2015. Uses a USB type-C cable that supports USB 3.1 (10 Gbps), Display Port (dual 4k displays), 4 lanes PCI Express 3.0 and previous versions of Thunderbolt. In addition, it provides 15 watts of power for connected devices and supports USB power for charging laptop computers up to 100 watts. Active copper and fiber optic cables support data transfer rates of up to 40 Gbps. Less expensive passive copper cables support speeds up to 20 Gbps. The first products using Thunderbolt 3 are expected to appear at the end of 2015. Many more devices will become available in 2016.
USB
USB 3.1
In July 2013, the USB 3.0 Promoter Group announced the creation of the USB 3.1 specification. New interface allows you to work at a speed of 10 Gbps and is fully compatible with previous versions of USB. USB 3.1 uses a 128b/132b encoding scheme, in which 4 bits are used to control the protocol and carry cable information. Devices using USB 3.1 with the new Type-C cable have already appeared on the market.
USB power
USB is an interface that can power connected devices, and more and more devices are being charged or powered by USB. The USB Power Delivery (PD) specification version 1.0 appeared in July 2012. It proposed increasing the power supply from 7.5 watts to 100 watts, depending on the type of cable and connector. Devices must negotiate with each other to determine the voltage and current to transmit electricity, and it is possible to transmit energy in any direction. Devices can adjust power supply while transmitting information. Prototypes of devices with USB PD began to appear at the end of 2013. The USB PD specification is included in the USB 3.1 specification.
USB Type-C cable
The specification for the new cable and connector was completed in August 2014. This cable has a significantly different design with a reduced connector size that can easily be used in a variety of devices. According to the new specification, the cable and connector can be used in any position, regardless of the orientation of the connector and the direction of the cable. The cable has the same type of connector on both sides. The first Type-C USB cables are passive copper cables up to 1 m long, with active copper and fiber optic cables expected soon.
Let's consider the RS-485 protocol as a serial industrial data transfer interface in automation equipment.
The Electronics Industry Association (EIA) RS-485 standard is a widely used industry standard for bidirectional, balanced transmission line. Protocol standard
EIA RS-485 has the following characteristics:
Maximum line length within one network segment: 1200 meters (4000 feet);
Bandwidth – 10 Mbaud and above;
Differential transmission line (balanced symmetrical lines);
The maximum number of nodes per segment is 32;
Bidirectional communication line with arbitration function operating over cables consisting of one twisted pair;
Possibility of connecting parallel nodes. True multi-drop connection design.
ADAM modules are completely isolated and operate on a single twisted pair cable when transmitting and receiving data. Since the nodes are connected in parallel, the modules can be freely disconnected from the host (system) computer without any consequences for the functioning of the remaining nodes. The use of shielded twisted pair cables in industrial environments is preferred because it provides a high signal-to-noise ratio.
At working together nodes in the network, there are no data transmission conflicts in it, since a simple command/return value sequence is used. There is always one exchange initiator (without an address) and a large number of passive nodes (with an address) in the network. In our case, the arbitrator is Personal Computer, connected via its serial RS-232 port to an ADAM-type RS-232/RS-485 network converter. ADAM modules act as passive participants in data exchange. When modules are not transmitting data, they are in a waiting state. The host computer initiates data exchange with one of the modules by implementing a command/return value sequence. The command usually consists of the address of the module with which the host computer wants to communicate. The module with the specified address executes the command and transmits the return value to the system computer.
The multi-current RS-485 network structure operates on the basis of a two-wire connection of nodes in a network segment. The docking modules will be connected to these two lines using so-called drop cables. Thus, all connections are made in parallel and any connections and disconnections of nodes do not in any way affect the operation of the network as a whole. Since ADAM modules work with the RS-485 standard and use commands in ASCII code format, they can interface and exchange information with any computers and terminals that accept these codes. When organizing a network based on the RS-485 protocol, connection schemes can be used: daisy chain, star, mixed, etc.
The block diagram of the communication system, which includes receivers and shapers that meet the requirements of this standard, is shown in Fig. 22. The elements of the system are drivers, receivers, connecting cable and matching resistors (R c). The total load due to the presence of receivers and drivers in a passive (on, high-impedance) state is determined by the number of load units present. The load unit, in turn, is determined by the current-voltage characteristic (volt-ampere characteristic). The load is the driver (G), the receiver (R) or their parallel connection in a passive state (Fig. 12).
Each case of uneven line impedance leads to reflection and distortion of the transmitted signal. If impedance unevenness occurs in the transmission line, it immediately results in a signal reflection effect that distorts the original signal. This effect is especially evident at the ends of lines. To eliminate unevenness, install a matching resistor at the end of the line.
INTERFACE (interface). A set of rules for the interaction of devices and programs with each other or with the user and the tools that implement this interaction. The concept of interface includes both the hardware and software, connecting various devices or programs between each other or with the user, as well as the rules and algorithms on the basis of which these tools are created. For example, device interface- these are communication lines between them, and interface devices, and a method for converting signals and data transmitted from device to device, and physical characteristics communication channel. Software interface- these are programs that service the transfer of data from one task to another, and data types, and a list of common variables and memory areas, and a set of valid procedures or operations and their parameters. User interface with the program- these are the buttons, menus and other controls displayed on the terminal screen, with the help of which the user controls the solution of the problem, and the terminal itself and the operators provided in the program that allow such control to be carried out.
User interface- in this chapter this means communication between a person and a computer.
In many definitions, an interface is identified with a dialogue, which is similar to a dialogue or interaction between two people. And just as science and culture need rules for people to communicate and interact with each other in dialogue, human-machine dialogue also needs rules.
General User Access are rules that explain dialogue in terms of general elements, such as rules for presenting information on a screen, and rules of interactive technology, such as rules for a human operator's response to what is presented on a screen.
INTERFACE COMPONENTS
On a practical level, an interface is a set of standard techniques for interacting with technology. At a theoretical level, the interface has three main components:
· A method of communication between a machine and a human operator.
· A method of communication between a human operator and a machine.
· Method of user interface presentation.
MACHINE TO USER
The way the machine communicates with the user (representation language) is determined by the machine application (application software system). The application controls access to information, processing of information, and presentation of information in a form understandable to the user.
USER TO MACHINE
The user must recognize the information the computer is presenting, understand (analyze) it, and proceed to the answer. The answer is implemented through interactive technology, the elements of which can be such actions as selecting an object using a key or mouse. All this makes up the second part of the interface, namely the action language.
HOW THE USER THINKS
This part of the interface is a set of user perceptions about the application as a whole, which is called user conceptual model.
Users may have an idea about machine interface what it does and how it works. Some of these beliefs are formed in users through experience with other machines, such as a printing device, a calculator, video games, and a computer system. A good user interface takes advantage of this experience. More developed ideas are formed from the user's experience with the interface itself. The interface helps users develop views that can later be used when working with other application interfaces.
User Interface Development: What does it mean?
The design of the site, the arrangement of functional blocks, the content and arrangement of the content are done in such a way that the user is pushed to perform the necessary action: calling, writing a comment, making a purchase, ordering a product, etc. It is worth understanding that user behavior is not adjusted or changed in any way. The site itself is undergoing transformation.
User interface– the order of arrangement of functional blocks of the site, facilitating the performance of certain actions by the user. This could be a call, purchasing a product, writing a review. A usability assessment can provide the same result. But these concepts should not be confused: usability differs from the user interface in that it is a method that allows you to evaluate the ease of use of a site and the user’s success in completing tasks. While interface design is a completely finished website prototype. Design involves using usability results. Without the data obtained by applying this technique, nothing will work.
