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Digital Buffer

Digital Buffer

The digital buffers are used in digital circuits for the amplification of digital signals in order to drive high current loads. Besides current amplification, the digital buffers provide isolation between input and output circuits where output is connected to some high-power load such as a relay, lamp or solenoid, etc. The digital device used for such purposes is called Digital Buffer.

The digital buffer is similar to the logic “NOT” gate in a way that it is a two-terminal device having input and output terminals only. However, the logic “NOT” gate complements the input signal at its output. As discussed in the logic “NOT” gate article, when the input of a “NOT” gate is “HIGH” then its output will NOT be “HIGH”. Likewise, when the input of a “NOT” gate is “LOW” then its output will NOT be “LOW”. On the other hand, the digital buffer does not complement the input signal at its output.  The input signal is reflected at the output of a digital buffer without any change in its logic. The digital buffer is a non-inversion logic and follows Idempotent Law. Its Boolean expression is given below:

Q = A

From the expression, it is eminent that the output (Q) state of a digital buffer is only true when the input (A) is true otherwise the output (Q) is false. The symbol and truth table of a digital buffer is shown below:

Digital Buffer
Figure 1: Digital Buffer symbol

Truth table of a Digital Buffer

Construction using NOT Gates

The digital buffer can be constructed using a basic logic “NOT” gate. The connection of two logic “NOT” gates back-to-back in series form a Digital Buffer. First, the “NOT” gate inverts the input signal, and second, “NOT” inverts the inverted signal back to the original input signal. The process of “double inversion” leads to the formation of a Digital Buffer.

Digital Buffer using NOT gates
Figure 2: Digital Buffer constructed using logic “NOT” gates

Digital Buffer Fan-out

The Digital Buffer is used in digital circuits even though it does not perform any logic or decision. The Digital Buffer is useful in the isolation or separation of two circuits whereas the impedance of the input circuit does not affect the impedance of the output circuit. Moreover, it can be used to drive high current loads such as switches or relays, etc. This means that Digital Buffers have the “fan-out” capability to deliver high power to the output loads.

The “fan-out” is the ability of a Digital Buffer or Digital I.C. to deliver high output current to a load. It is simply, the capability to amplify the input signal at its output after performing any due logic. The output of a logic gate may need to be connected to a high current LED, switch or relay and in such a case a logic gate with a high “fan-out” is required. Usually, the output of a logic gate is connected to the input of another logic gate and it requires a nominal current to drive another gate’s input. When a number of inputs (logic gates) are connected to the output of a logic gate then additional current is required which depends upon a number of factors such as the number of inputs and their circuit types etc. In simple words, it can be said that the “fan-out” is the number of parallel connections that can be efficiently driven by a logic gate or Digital Buffer.

Fan-out example
Figure 3: “Fan-out” example using a Digital Buffer



Generally, a Digital Buffer can have a high “fan-out” rating of 20 to drive parallel connections of the same logic family. A Digital Buffer with a high fan-out (current source) rating also carries a high fan-in (current sink) rating. However, there is a limitation to the number of devices that can be connected to the input or output of a logic gate due to propagation delay. The propagation delay is a function of the number of connections taken out of a terminal and it deteriorates with the increase in the number of signals.

Tri-state Buffer

The Tri-state Buffer, as the name says, has three states that can be achieved by an electronic controller connected to an input terminal of Digital Buffer. The Tri-state Buffer is used in circuits where decoupling of input and output circuits is essentially required. It is a device similar to the Digital Buffer but has three terminals and the additional (third) terminal is used to control the output of Digital Buffer. Additionally, it has three states compared to the two states of a Digital Buffer.

The Tri-state Buffer’s output (Q) can be put into any of the three states by electronically driving its “Control” or “Enable” terminal to logic “LOW” or “HIGH”. It can be thought of as an input controller switch which is demonstrated in the following figure.

Tri-state Buffer using switch example
Figure 4: Tri-state Buffer states

The Tri-state buffer can be activated or deactivated using the “Enable” terminal. When enabled, the Tri-state Buffer reflects the input signal towards the output without any change just like a Digital Buffer. Whereas, when Tri-state Buffer is disabled then path between input and output becomes open-circuited and leads to a high impedance state “Hi-Z”. This high impedance state “Hi-Z” is the third-state besides logic “HIGH” and “LOW” states. Because of these three states, it is called a Tri-state Buffer.

In the high impedance “Hi-Z” state, a high impedance appears between input and output leading to electrical isolation. In this state, no current flows in the input and from the output.

The Tri-state Buffer discussed above is an Active “HIGH” Tri-state Buffer as it becomes active when “Enable” is at a “HIGH” state. Another variant is an Active “LOW” Tri-state buffer which gets activated when “Enable” is at a “LOW” state. These Tri-state Buffers are non-inverting when enabled and reflect the input signal at the output without inversion. However, Tri-state inverting Buffers are also commercially available which inverts the input signal at the output. They are also available in Active “HIGH” inverting and Active “LOW” inverting Tri-state Buffer variants. These four types of Tri-state Buffer variants are explained below along with their truth tables.

Active “HIGH” Tri-state Buffer

The symbol and truth table of Active “HIGH” Tri-state Buffer is shown below:

Figure 5: Active “HIGH” Tri-state Buffer

The active “HIGH” Tri-state Buffer is commercially available as 74LS241 with octal buffers. It is active when the “Enable” terminal is at a “HIGH” state and passes the input signal towards the output unaltered. When the “Enable” terminal is at the “LOW” state then Tri-state Buffer becomes disabled and a high impedance state “Hi-Z” appears at the output.

Active “LOW” Tri-state Buffer

The symbol and truth table of Active “LOW” Tri-state Buffer is shown below:

Figure 6: Active “LOW” Tri-state Buffer

The active “LOW” Tri-state Buffer is active when the “Enable” terminal is at a “LOW” state and passes the input signal towards the output unaltered. When the “Enable” terminal is at the “HIGH” state then Tri-state Buffer becomes disabled and a high impedance state “Hi-Z” appears at the output. The “Inversion Bubble” at the terminal of “Enable” indicates an active “LOW” input.

Active “HIGH” Inverting Tri-state Buffer

The symbol and truth table of Active “HIGH” Inverting Tri-state Buffer is shown below:

Figure 7: Active “HIGH” inverting Tri-state Buffer

The active “HIGH” Tri-state Buffer is commercially available as 74LS240 with octal buffers. It is active when the “Enable” terminal is at a “HIGH” state and passes the input signal towards the output after inversion. When the “Enable” terminal is at the “LOW” state then Tri-state Buffer becomes disabled and a high impedance state “Hi-Z” appears at the output. The “Inversion Bubble” at the output terminal indicates an inversion of the input.

Active “LOW” Inverting Tri-state Buffer

The symbol and truth table of Active “LOW” Inverting Tri-state Buffer is shown below:

Figure 8: Active “LOW” inverting Tri-state Buffer

The active “LOW” Tri-state Buffer is active when the “Enable” terminal is at a “LOW” state and passes the input signal towards the output after inversion. When the “Enable” terminal is at the “HIGH” state then Tri-state Buffer becomes disabled and a high impedance state “Hi-Z” appears at the output. The “Inversion Bubble” at the output terminal indicates an inversion of the input. Whereas, “Inversion Bubble” at the terminal of “Enable” indicates an active “LOW” input.

Tri-state Buffer as Bus Controller

The Tri-state Buffers are used in many electronic and digital circuits to control access to the data buses allowing multiple devices to be connected to the single data bus. The data buses exist between microprocessors, peripherals, I/O or memory chips, etc. and multiple devices interface with them. The multiple devices connected with the same bus tries to fetch the bus to “LOW” or “HIGH” creating a contention. The contention is said to occur when some of the devices try to pull up (HIGH) the bus whilst at the same time some devices try to pull it down (LOW). This would create a condition of short-circuiting and could cause damage to the delicate circuitry.  The Tri-state Buffer is used to control the interface/ access between the device and bus. It connects or isolates the interface using the “Enable” line and connects the desired device at a time to the bus. In the following figure, a common data bus is connected to the four data-in lines and two-bit data-out lines.

Data bus example using Tri-state Buffers
Figure 8: Data Bus access example using Tri-state Buffers

Using “Enable” lines of four data-in lines, any one of them can be connected to the data bus and its desired output (data-out) can be selected in a similar way. In this scheme, a total of six devices are connected to the common data bus and each of them can utilize this bus to route their data to different devices/ peripherals at the output.

Tri-state Buffer Control

The multiple Tri-state Buffers can be controlled using a digital decoder. The digital decoder, such as a Binary Decoder, has a number of binary inputs and selects the appropriate decoder output depending on the binary input signals. The Tri-state Buffers connected to that specific decoder output becomes active only whilst others remain at the “Hi-Z” state. Another state of binary inputs leads to a change in decoder output and another set of Tri-state Buffers interfaces the data bus. Meanwhile, other Tri-state Buffers become isolated. In the following figure, a 4-bit data bus is shown to be connected with four different data sets using a binary decoder.

4-bit data bus example using tri-state buffers
Figure 9: A 4-bit data bus interface example using Tri-state Buffers

In the above figure, Data Set A gets connected to the common data bus when inputs are at state “00”. In the same way, Data Sets B, C, and D make an interface with the bus when inputs are at “01”, “10”, and “11” states, respectively.

Commercially Available Buffers

  • CMOS based Buffers
  • CD4050 Hex Non-inverting Buffer
  • CD4503 Hex Tri-state Buffer

TTL based Buffers

  • 74LS07 Hex Non-inverting Buffer
  • 74LS244 Octal Buffer

In the following figures, a Digital Buffer (74LS07) and Octal Tri-state Buffer (74LS244) are shown.

Figure 10: TTL “74LS07” HEX Digital Buffer package
Figure 11: TTL “74LS24” Oct Tri-state Buffer package

Conclusion

  • The Digital Buffer is a simple two-terminal device that is used for the amplification of digital signals.
  • The Digital Buffer isolates the input and output circuits so that their impedances do not affect each other.
  • The Digital Buffer can be non-inverting or inverting and, in the case of inverting, an inverted signal of input appears at the output.
  • The Digital Buffers have high “fan-out” and “fan-in” capability which means that a number of devices can be connected at the input and output. Because of the high “fan-out” (current source) rating, a high current LED, switch, or relay can be driven through it.
  • The Tri-state Buffer has an additional input terminal called “Enable” and a high impedance state “Hi-Z” compared to the Digital Buffer.
  • The Tri-state Buffer output can be controlled through the “Enable” line leading to coupling and decoupling of input and output circuits. In disable or decouple state, a high impedance state (Hi-Z) appears between input and output terminals of the Tri-state Buffer.
  • The Tri-state Buffers are commercially available in Active “HIGH” Non-inverting, Active “LOW” Non-inverting, Active “HIGH” Inverting, and Active “LOW” Inverting variants.
  • The Tri-state Buffers are used in microprocessors or digital circuits to control the interfaces of data buses between devices.
  • The Tri-state Buffers control can be driven using a Decoder which enables or disables a set of Tri-state Buffers depending upon the decoder output.

CN0531 – Programmable 20-Bit, Linear, Precision, Bipolar ± 5V DC Voltage Source

Posted on by mixos

Precision dc voltages are a critical component of scientific instrumentation and measurement equipment, automated test equipment, factory automation and control, chemical analysis, and many other high precision applications. The most demanding applications require single digit, part per million temperature drift, subppm linearity, and low, predictable noise performance.

The circuit shown in Figure 1 is a programmable 20-bit voltage source that enables these demanding applications. The output range is −5 V to +5 V with ±1 LSB integral nonlinearity (INL), ±1 LSB differential nonlinearity (DNL), and exceptionally low noise and low drift across the entire output range.

On-board power converters produce the required supply rails from a single voltage supply provided by the development platform board. Low noise, high power supply rejection ratio (PSRR) voltage regulators ensure that the switching noise is minimized. A high precision, high stability, on-board hermetically sealed voltage reference ensures the high precision and accuracy of the 20-bit system.

Features:

  • +/-5V Output Range
  • 20-Bit Signal Generation Control
  • On board precision 5V Reference
  • All Power Rails Generated Using a Single 3.3V Source

The output of the circuit is a buffered voltage with an option for a remote sense connection to compensate for lead resistance or allow for the insertion of an external power stage, if necessary, providing drive flexibility for the desired end application.

more information: https://www.analog.com/en/design-center/reference-designs/circuits-from-the-lab/cn0531.html

SiC power FETs boast super-low 6-mΩ RDS(on)

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At an RDS(on) value of less than half the nearest SiC MOSFET competitor, a new 6-mΩ device also provides a robust short-circuit withstand time rating of 5 μsec. The new 750-V SiC FET series includes nine new device/package options rated at 6, 9, 11, 23, 33, and 44 mΩ. All devices are available in the TO-247-4L package while the 18, 23, 33, 44, and 60 mΩ devices also come in the TO-247-3L. Complemented by the already available 18 and 60-mΩ devices, this 750-V expanded series provides designers with more device options, enabling more design flexibility to achieve an optimum cost/efficiency trade-off while maintaining generous design margins and circuit robustness.

Gen 4 SiC FETs from UnitedSiC are a ‘cascode’ of a SiC JFET and a co-packaged silicon MOSFET. These together provide the full advantages of wide band-gap technology–high speed and low losses with high-temperature operation, while retaining an easy, stable, and robust gate drive with integral ESD protection. The advantages are quantified by Figures of Merit (FoMs) such as RDS(on)xA, a measure of conduction losses per unit die area. Gen 4 SiC FETs achieve the lowest values in the market at both high and low die temperatures. FoM RDS(on)xEOSS/QOSS is important in hard-switching applications and is half the nearest competitor value. FoM RxCOSS(tr) is critical in soft-switching applications and UnitedSiC device values are around 30% less than competitor parts, rated at 650 V compared with UnitedSiC’s at 750 V.

For hard switching applications, the integral body diode of SiC FETs is superior in recovery speed and forward voltage drop to competing Si MOSFET or SiC MOSFET technologies. Other advantages incorporated into the Gen 4 technology are reduced thermal resistance from die-to-case by advanced wafer thinning techniques and silver-sinter die-attach. These features enable maximum power output for low die temperature rise in demanding applications.

With their latest improvements in switching efficiency and on-resistance, the new UnitedSiC SiC FETs are candidates for challenging, emerging applications. These include traction drives and on- and off-board chargers in electric vehicles and all stages of uni- and bi-directional power conversion in renewable energy inverters, power factor correction, telecoms converters and AC/DC or DC/DC power conversion generally. Established applications also benefit from use of the devices for an easy boost in efficiency with their backwards compatibility with Si MOSFET and IGBT gate drives and established TO-247 packaging.

Pricing (1000-up, FOB USA) for the new 750-V Gen 4 SiC FETs range from $4.15 for the UJ4C075044K3S, to $23.46 for the UJ4SC075006K4S. All devices are available from authorized distributors.

AGS103T Ultra-Compact IoT Gateway Edge Computing System

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IBASE Technology Inc., a leading provider of industrial motherboards and embedded systems, rolls out AGS103T ultra-compact IoT gateway edge computing system integrating the Intel Atom® x6000E Series processors (code-named Elkhart Lake) that deliver up to 4 cores with 40% increase in CPU performance and improved graphics when compared with previous versions. Based on Intel’s 10nm technology, the energy-efficient platform is suitable for embedded applications in factory automation, IoT gateway, edge computing and automatic control systems.

AGS103T FEATURES:

  • Intel® Atom® x6413E/x6211E Series processors
  • GPIO 4-in/4-out & 1x DVI-I & 1x HDMI
  • Over/Under/Reverse voltage protection
  • Extended operating temperature from -20°C to 70°C
  • 9V~36V DC wide-range power input
  • 1x 3042/2242 M.2 B-Key, 1x Micro SD, optional 1x 2.5” SSD
  • 3x Gigabit Ethernet, 3x full-size Mini PCI-E sockets & 2x SIM card slots
  • 4x COM (RS232/422/485), 2x USB 3.1 & 2x USB 2.0
  • Supports DIN-rail mount, wall mount & TPM 2.0

The ruggedized AGS103T boasts several advanced features such as an extended operating temperature range of -20°C to 70°C, three Gigabit Ethernet ports for fast wired connections and multi-protocol communications, and over/under/reverse voltage protection. Useful I/O interfaces include 3042/2242 M.2 B-Key, Micro SD, four COM (RS232/422/485), two USB 3.1 and two USB 2.0 sockets.

In addition, the low-power AGS103T supports DIN-rail and wall mounting installation, and onboard TPM 2.0 hardware-based security to ensure platform integrity. It is available with Intel® Atom® QC x6413E or Intel® Atom® DC x6211E and with an option for additional storage for 2.5” drives. For more information, please visit www.ibase.com.tw.

The VPC-5620S: One Platform with Two Innovative Solutions Built for Industrial Edge Applications

Posted on by mixos

AAEON, a leader in embedded edge platforms, introduces the VPC-5620S industrial embedded system. Available in two builds, the slim VPC-5620S IS and in-vehicle VPC-5620S VS, the system leverages a modular design to combine the power 8th Generation Intel® Core™ processors with greater performance, storage capabilities and expansion support.

The VPC-5620S brings the performance of the 8th Generation Intel Core processors (formerly Whiskey Lake) to a rugged industrial platform designed to power embedded AI Edge applications anywhere they’re needed. With up to 64GB of memory, the VPC-5620S can power intelligent visual analysis applications such as Smart Factory and Security, and with expansion slots, can support AI accelerators to scale up the inference processing capabilities.

Available in two standard configurations, the VPC-5620S IS industrial system and VPC-5620S VS in-vehicle system, this versatile platform offers broad I/O features including four Smart PoE PSE ports designed for PoE cameras. Built to simplify the deployment of visual applications, the Smart PoE ports can be managed with a user-friendly interface, allowing users to control voltage outputs or turn ports on and off remotely. Additional I/O features include four USB3.2 Gen 1 ports, two COM ports, HDMI and 8-bit DIO. Thanks to the modular design of the VPC-5620S platform offers additional configurations available on a per-project basis.

The VPC-5620S offers expandability to help quickly add on functionality and storage flexibility. Wireless connectivity is supporting through two mPCIe slots, designed for Wi-Fi and LTE network deployments, along with an optional M.2 slot for 5G support. The system offers and M.2 slot with NVMe support for fast read/write speeds, as well as two 2.5” SATA drive bays in standard configuration to support local network storage needs, such as for NVR and AI Surveillance applications. Users can also utilize eMMC and mSATA storage options.

One key feature of the VPC-5620S is its rugged design. Built to operate in a wide range of environments, the system boasts an operating temperature range of -20°C to 70°C. The system is tested to MIL-STD-810G shock and vibration standards, and the fan-less design helps keep dust and contaminants out, ensuring long-lasting, consistent and reliable operation. Additionally, the VPC-5620S comes standard with wide voltage input, supporting 12 – 24V inputs.

With its modular design, the VPC-5620S platform delivers a range of flexibility unlike other systems. In addition to the standard VPC-5620S IS and VPC-5620S VS systems, the VPC-5620S offers several optional configurations. AAEON offers additional service and support to help provide customization and configuration support to users and developers, helping meet the exact needs of their applications.

more information: AAEON.com

TPS2116 1.6 V to 5.5 V, 40 mΩ, 2.5 A, Low-IQ Priority Power Multiplexer

Posted on by mixos

Texas Instruments’ power mux features manual and priority switchover

Texas Instruments TPS2116 is a power mux device with a voltage rating of 1.6 V to 5.5 V and a maximum current rating of 2.5 A. The device uses N-channel MOSFETs to switch between supplies while providing a controlled slew rate when voltage is first applied.

The low quiescent of 1.32 µA (typical) and a low standby current of 50 nA (typical) make the TPS2116 ideal for systems where a battery is connected to one of the inputs. These low currents extend the life and operation of the battery when in use. The TPS2116 can be configured for two different switchover behaviors depending on the application. Automatic priority mode prioritizes the supply connected to VIN1 and switches over to the secondary supply (VIN2) when VIN1 drops. Manual mode allows the user to toggle a GPIO or enable a signal to switch between the channels.

Features

  • Input voltage range: 1.6 V to 5.5 V
  • Continuous current: 2.5 A (max.)
  • On resistance: 40 mΩ (typ.)
  • VIN2 standby current: 50 nA (typ.)
  • Quiescent current: 1.32 µA (typ.)
  • Thermal shutdown
  • Switchover modes: priority mode and manual mode
  • Controlled output slew rate: 1.3 ms (typ.) at 3.3 V
  • Reverse current blocking when VOUT > VINx

more information: https://www.ti.com/product/TPS2116

Analog Style VU Meter on OLED Display – Arduino Compatible

Posted on by mixos

This is an analog-style VU meter on a 0.96″ OLED Display. The project has a 0.96″ OLED display, Atmega328 Microcontroller, 3.5 mm audio EP socket for audio signal input. This Arduino compatible hardware can be program using Arduino IDE. Operating Supply 5V DC.

Analog Style VU Meter on OLED Display – Arduino Compatible – [Link]

s-Sense modules from R&D SOFTWARE SOLUTIONS

Posted on by mixos

TME’s offer features miniature modules for monitoring environmental conditions from R&D SOFTWARE SOLUTIONS. The manufacturer offers the modules in several different variants differing in terms of the number and type of embedded sensors.

You can select from pressure sensors, temperature sensors, humidity sensors, CO2 sensors and VOC (Volatile Organic Compounds) sensors. The systems are powered within the range of 3.3V DC to 5V DC, which means they can be used with the most common platforms, such as Arduino, Banana Pi, Raspberry Pi, Beagle Bone, or Teensy.

The I2C communication requires the use of two microcontroller lines, regardless of the number of connected modules. This makes R&D SOFTWARE SOLUTIONS products useful even in basic systems with a limited number of pins.

Specifications

  • Communication standard: I2C
  • Available sensors, CCS811 , HDC2010 , BME280, BME680, BMP280
  • Supply voltage: 3.3/5V DC
  • Operating temperature: -40⁰C to +80⁰C
  • Dimensions: 13x27mm
  • Weight: (without wires) 2g

more information: s-Sense modules »

12VDC to 220-380VDC Converter

Posted on by mixos

When powering many appliances from a sine wave inverter, the HV DC is converted to AC only to be rectified back to DC in the appliance.

This inverter eliminates the SPWM stage and outputs DC only. This DC can be used to power appliances, or as a HV DC source for your SPWM, variable frequency drive (.. for your inverter fridge) or other project.

Ebay, AliExpress and other like stores have cheap 12VDC to 220-380VDC Converters (pictured above), ready for purchase under board names like QS-100 and GZF-02-Y.

These basic converter boards consist of a SG3525, four IRF3205 MOSFETs and a Transformer. They include no overload protection, output regulation/feedback or DC rectification. Nor do they include low voltage cutouts.

This project intends to build upon these boards and build in these other features and protection.

The converter uses a prewound 500W Transformer available from AliExpress.

This project requires a vertically mounted driver card – 12VDC to 220-380VDC Converter Driver Board (Closed Loop) or 12VDC to 220-380VDC Converter Driver Board – Open Loop.

by Craig Peacock @ circuitmaker.com

Win an Arduino Nano 33 IoT

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Small, robust and powerful board with Wi-Fi and Bluetooth connectivity combined with its low power architecture makes it a practical solution.

This month oemsecrets.com has teamed up with Farnell to giveaway an Arduino Nano 33 IoT development board to two lucky winners. Simply follow the link below to enter.

Get extra entries into the giveaway by following us and sharing this article on Instagram, LinkedIn, Facebook or Twitter using #oemsecrets or @oemsecrets.

ENTER NOW

Arduino Nano 33 IoT

The Arduino Nano 33 IoT is the easiest and cheapest point of entry to enhance existing devices (and creating new ones) to be part of the IoT and designing pico-network applications. Whether you are looking at building a sensor network connected to your office or home router, or if you want to create a BLE device sending data to a cellphone, the Nano 33 IoT is your one-stop-solution for many of the basic IoT application scenarios.

The board’s main processor is a low power Arm® Cortex®-M0 32-bit SAMD21. The WiFi and Bluetooth® connectivity is performed with a module from u-blox, the NINA-W10, a low power chipset operating in the 2.4GHz range. On top of those, secure communication is ensured through the Microchip® ECC608 crypto chip. Besides that, you can find a 6 axis IMU, what makes this board perfect for simple vibration alarm systems, pedometers, relative positioning of robots, etc.

Update 01/10/2021

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