A transceiver within radio communication is a communication device, used to transmit & receive radio signals through an antenna for communication purposes. This is a combination of a radio transmitter (Tx) & a receiver (Rx), used in wireless devices. Not like the buffer, these devices are bidirectional that allow data to supply throughout them in any direction. Similarly, an octal bus transceiver is mainly designed for asynchronous communication in two ways between two data buses. This article discusses an overview of the 74HC245 octal transceiver IC–pin configuration, specifications, working, and applications.
What is the 74HC245 Octal Transceiver?
74HC245 is an octal transceiver IC used to transmit asynchronous data between two devices. This transceiver IC supports the transmission of data at various voltage levels. This IC includes two amplifiers, so it performs two-way communication which can be attained through an applied signal on the direction control pin.
This chip is frequently used as a bus buffer or logic-level translator. This IC has 8-bit data lines & bi-directional transfers, appropriate to change from one logic level signals to other logic level signals mainly for communication between different logic levels or families.
74HC245 Octal Transceiver IC
The 74HC245 octal transceiver IC includes three-state outputs, which means it includes two sets of pins from A0 to A7 & B0 to B7 where every set includes 8 pins. From these two sets of pins, one set is used as input & remaining set is used as output. Since this is a transceiver chip, the data supplies from the i/p bus to the o/p bus & also from the o/p bus to the i/p bus by toggling simply the DIR (Direction pin) as necessary.
This IC establishes communication protocol buses like I2C, SPI, and many more in between two different MCU or MPUs by different operating voltages because this IC has a maximum speed buffer.
Pin Configuration:
The pin configuration of 74HC245 IC is shown below. This IC has 18 pins and each pin functionality is discussed below.
74HC245 Octal Transceiver PinOut
Pin1 (DIR/Direction Control): This DIR pin helps in deciding the Data direction.
Pins 2 to 9 (Data Input/output (A0-A7)): The data I/O pins of amplifier A include from A0 to A7 which can be utilized as 8-bit I/O pins depending on the DIR pin condition.
Pin 10 (Ground/GND): It is a GND pin, connected to the GND of the system
Pins11 to 18 (Data I/O (B0-B7)): These data I/O pins of amplifier B mainly include from B0 to B7 which are used as 8-bit I/O pins based on the DIR pin condition.
Pin 19 (Output Enable/OE): It is an active low pin, used for enabling or disabling input.
Pin20 (Voltage Supply/Vcc): It is a differential analog i/p that is connected to the input of ADC.
Features & Specifications:
The features and specifications of 74HC245 IC include the following.
- It is an 8-bit transceiver including three state o/p.
- Its voltage supply ranges from 2 volts to 6 volts.
- Its minimum i/p voltage is 0.8V.
- Its maximum i/p voltage is 4.2V.
- Its min o/p voltage is 1.9 volts.
- Its maximum o/p voltage is 5.4V.
- Its o/p current is 35mA.
- Its quiescent current is 80μA.
- Its non-state o/p current is 10uA.
- Its low i/p current is 1A.
- Its o/p drive capacity drives 15 LSTTL loads.
- Its propagation delay is 13 ns.
- Its package is 20-pin SSOP20, SO20, DHVQFN20 & TSSOP20.
- It is very simple to interface.
Equivalent & Alternative Transceiver ICs
The equivalent 8-bit 74HC245 IC is SN74S245 whereas alternative 74HC245 transceiver ICs are; MCP2515, MCP2551, SN7516, etc.
Working of 74HC245 Octal Transceiver
74HC245 IC provides an output of either 0 or 1, so it is mainly designed for digital only. Sometimes the two pieces of hardware communicating have different operating voltages. In these cases, a voltage divider or any other logic-level converter can be used. This 74HC245 IC is mainly responsible for the communication from one bus to another bi-directionally based on the control input direction.
Once the low logic level is applied, the data at the input of the first amplifier within the IC flows toward Bus A. Similarly, whenever a high logic level is applied, the data at the input of the first amplifier will flow toward Bus B. This octal transceiver IC has one more control input like OE (Output Enable).
This OE control input separates the two buses from each other. When a high logic level is applied to this input will cause the o/p to be in a higher impedance condition & disables the o/p which is used to enable & disable the output.
Functions
The main functions of the 74HC245 octal transceiver are discussed below.
Translation of Logic Level
This octal transceiver is capable of converting a signal from the TTL family to the required level by another CMOS logic family. So this allows different kinds of logic circuits to be allied & communicate in a similar system.
Bus Buffer
This IC can be used as a bus buffer for transmitting data from one bus to another bus by simply maintaining the integrity & stability of the signal. So this is extremely significant for data transfer as well as communication in between several modules or devices.
Data Transmission in Two-ways
The data transmission can be done between i/p & o/p through the function of two-way transmission. So this is helpful in applications that need bidirectional data transmission like bus communication & bi-directional data lines connection.
Data Line Drive
This octal transceiver provides sufficient current & voltage by very strong o/p drive capacity to drive the logic circuits or receiver.
How to use the 74HC245 IC?
Generally, MSP430 and Raspberry Pi works with 3.3Volts but other types of integrated circuits or sensors like TFT LCD displays, Ultrasonic sensor, etc works with 5Volts. In such situations, we have to move one set of operating voltage to another set from 3.3V to 5V. For that, we use a logic level converter which is a potential divider. But it is not capable of high-speed operation or bi-directional communication buses. Therefore in those cases, a 74HC245 bi-directional transceiver IC is an ideal choice. The logic level converter circuit using 74HC245 IC is shown below.
74HC245 Octal Transceiver Circuit
By using this circuit, we can convert the data lines from 3.3V to 5V. The Data can be made to supply in two directions by simply controlling the AB/BA (DIR). In addition, we can also decrease the input leakage current by simply disabling the inputs with the OE pin. The o/p voltage will be equivalent to the Vcc voltage always, so since we are changing the voltage from 3.3V to 5V, we must power the Vcc pin by +5V.
In the above circuit, the microcontroller works at 5Volts & you require to communicate by a device that works at 3.3Volts. A 74HC245 IC is used for interfacing between the two levels of voltage. Here, the microcontroller provides output data toward the A-pins of the octal transceiver IC and this data can be buffered & transferred to the B-pins at a low-level voltage. Likewise, the 3.3V device’s data can be given as input into the B pins & at the higher level of voltage, it is transmitted to the microcontroller.
Where to use 74HC245 Octal Transceiver / Applications
The applications of the 74HC245 IC octal transceiver include the following.
- The 74HC245 three-state non-inverting transceiver IC is used for asynchronous data transfer between two devices or different data buses.
- These ICs are used in real-life applications like servers, telecom infrastructures, electronic points of sale, personal computers, network switches, wearable health devices, notebooks, and many more.
- This octal transceiver IC is used to address bus buffers, data bus transceivers, logic level converters, and driver IC mainly for communication protocols.
- 74HC245 IC is common in different digital electronic projects like microcontrollers interfacing with other types of devices like LCD displays, motors, sensors, etc.
- This IC can also be very useful in isolating different elements of a system otherwise for interfacing different voltage levels.
- 74HC245 IC is widely used in wireless communications and networking applications.
- This IC can be used on a CPU board to buffer data on a bi-directional bus otherwise to drive small loads.
Please refer to this link for the 74HC245 Octal Transceiver Datasheet.
Thus, this is an overview of 74HCT245 octal transceiver IC. This is the most frequently used logic level converter & bus buffer that performs signal conversion as well as transmission of data between different logic levels. So this IC is used widely in the communication & digital system design field. Here is a question for you, what is asynchronous communication?