SN74LS245DW

1. Pinout Description

SN74LS245DW is a 20-pin dual in-line package ic, as indicated in the following diagram. It is composed of eight data elements, eight direction control elements and four control elements. Each data element is composed of an output port, an active low direction control port (DIR), and an active low tri-state output port (OE). The peripheral devices, such as keyboard, printer, memory, and other peripheral equipment, can be connected to the Data bus, and SN74LS245DW will convert their parallel input/output to serial output.

2. Working Principle

SN74LS245DW works as a bidirectional transceiver that transfers data or address information from one device to another. It is a 8-bit device that can transmits 8 parallel bits through 8 channels and controls the 8 channels through 4 control signals. The working principle is quite simple. During the period of data transmission, firstly, the data output from the input port of SN74LS245DW is connected to 8-bit parallel data bus, then, the DIR control signal is set to low, since the direction port of each channel is connected to the DIR control terminal, thus all the channels are set to output mode, and the data from the data bus is transferred to output port. If the input port receives data, the host sets the DIR control signal to high to make the channel in the input mode. The data output from the host is transferred to the data bus and then it is connected to the input port of SN74LS245DW, thus the data transmission is completed.

3. Applications

SN74LS245DW has wide application in the data transmission field, such as connecting two microprocessors, computers or other peripheral devices. It is mainly used in instrumentation, robotics, telecommunications and many other applications. In addition, it can be used as a driver that outputs selected data bit from a bidirectional bus, as a multiplexer that enables simultaneous data transmission from 8-bit data bus to 1-bit serial output, and as a DMA controller or a microprocessor peripheral.

4. Strengths and Weaknesses

SN74LS245DW was designed to have low power consumption and provide high noise immunity, and it has high speed performance. The device can work with relatively low supply voltage, which reduces the cost significantly, and the fast speed provides better performance for applications that require quick and accurate data transmission. Although the device has high performance, it has some drawbacks, such as the lack of internal Schmitt triggers and lack of signal conditioning circuits. This makes it unsuitable for signal applications that require signal conditioning circuit.