74HC573 Transparent Latch Functions, Working Principle, Usage and Application
28 December 2023
Ⅲ. Pin configuration of 74HC573 latch
Ⅴ. How does 74HC573 latch work?
Ⅶ. Practical application of 74HC573 in circuits
Ⅷ. Can 74HC245 replace 74HC573?
The 74HC573 is a high performance silicon gate CMOS device. This article mainly discusses the 74HC573 latch from the aspects of pin configuration, functions, working principle, usage and applications.
A latch is an electronic circuit in an asynchronous sequential logic circuit system in a digital circuit that is used to store information. It can only store one bit of information and is usually used with multiple latches. Some latches have special names, such as "4-bit latches" (can store four bits of information) or "8-bit latches" (can store eight bits of information), etc.
The 74HC573 stands as a high-performance silicon gate CMOS device, boasting eight D-type transparent latches, each equipped with an independent D-type input and three-state outputs tailored for bus-oriented applications. These latches are interconnected through a latch enable (LE) terminal and an output enable (OE) terminal, fostering efficient coordination. Its widespread utilization spans across computers, where it contributes to data storage and processing, communications, facilitating information exchange, and industrial control applications, where precision and reliability are paramount .
Alternatives and equivalents:
• CD4099
The pins of 74HC573 are shown in the figure above. Among them, its pin name and description are as follows.
• OE: Output enable
• LE: Latch enable
• D0~D7: Data input pins
• Q0~Q7: Data output pins
• GND: Ground terminal of ground wire
• VCC: Supply voltage
74HC573 is a device with eight 3-wire pins, including two input ports and one output port. The device is divided into two independent 4-bit ports, each port contains an input port and an output port, and can be used to process 8-bit data. The input port is a bidirectional pin, so the input data can be either bidirectional or unidirectional. It has an internal self-clearing eight-bit memory that can store an 8-bit binary bit sequence. 74HC573 uses TTL-compatible low-level input, outputs high-speed pulses up to 25MHz, and has strong driving capability and low power consumption. In addition, the chip features high-speed conversion and chip protection, making it more efficient when processing 8-bit data.
The eight latches of the 74HC573 are all transparent D-type latches. When enable (G) is high, the Q output will follow the data (D) input. When enable is low, the output will latch at the established data level. Output control does not affect the internal working of the latch, that is, old data can be retained, and new data can be placed even when the output is turned off. This kind of circuit can drive large capacitance or low impedance loads, and can directly interface with the system bus and drive the bus without the need for an external interface. This applies particularly to buffer registers, I/O channels, bidirectional bus drivers and working registers.
When using the 74HC573 chip for data transmission, we usually need to connect its input pins (D0-D7) to the output pins of the CPU or other peripherals, and at the same time connect its output pins (Q0-Q7) to another input pin for a peripheral. When transmitting data, the CPU first writes the data to be sent to the input port of the chip, and then opens the output port of the chip through the enable port (OE) to transmit the data to other peripherals. For situations where data exchange between multiple sets of peripherals is required, we can use cascading to connect multiple 74HC573 chips.
When using the 74HC573 chip, we also need to pay attention to the following points. First of all, when we connect chips and other devices, we should use appropriate resistors, capacitors and other components to ensure the quality of the signal. Secondly, we should try to shorten the distance between the chip and each device to reduce signal delay and interference. Finally, before writing data, we should ensure that the original data in the latch has been cleared to avoid data errors and interference.
Take the pulse data acquisition circuit as an example. As shown in the figure, we use AT89S52 microcontroller with two 74HC573 latches to transmit information. AT89S52 has the advantages of low power consumption, high performance, 8K-byte Flash and 32-bit I/O port lines, full-duplex serial communication port, etc. Among them, the U10 latch is used for the bit selection function, and the U9 latch is used for the segment selection function. This configuration effectively expands the I/O port of P2 of the AT89S52 microcontroller, allowing program control information and pulse data information to be effectively controlled during the transmission process. This provides an important basis for the collection of multi-channel pulse data.
The 74HC573 and 74HC245 chips are both devices used for data storage and transmission. The main difference between them is how the output pin levels are controlled. The output port of the 74HC573 chip is a transparent port. Even if the clock signal does not cause the latch to latch, it will transfer the input data directly to the output pin. The output port of the 74HC245 chip is a three-state port, that is, when the input enable terminal is high level, the output pin is in a high impedance state. Therefore, there are certain differences between the two. But in some cases, they can be used interchangeably. For example, when we need to transmit data from one circuit board to another, we can use the 74HC245 chip for data transmission. When we need to maintain the storage status of data, we should use the 74HC573 chip.
Frequently Asked Questions
1. What is 74HC573?
74HCT573 is an 8-bit D-type transparent latch with 3-state outputs. The device features latch enable (LE) and output enable (OE) inputs. When LE is HIGH, data at the inputs enter the latches.
2. What is the difference between 74HC574 and 74HC573?
The 74HC573 is an octal D-type transparent latch where latch is activated when the LE output is high. The 74HC574 is an octal D-type flip flop with latched output activated by the positive edge of its LE output.
3. What is the power supply voltage range for the 74HC573?
The typical power supply voltage range for the 74HC573 is 2.0V to 6.0V.
4. What is the function of the 74HC573?
The 74HC573 is an octal transparent latch with 3-state outputs. It can store and output eight bits of data and is often used in digital electronic circuits for data storage and transfer.
