8-Bit/VLIO UARTs

Exar’s 8-bit UARTs are the industry’s largest UART product family offering devices from 1 to 8 channels and FIFO sizes up to 128 Bytes. Each UART has a parallel 8-bit bus interface. The UART offloads the serialization and de-serialization of the data from the MCU or processor. The enhanced features simplify hardware design and software development. The “Intel” interface has separate address, data, read and write lines. The “Motorola” interface has separate address and data lines, but the read/write lines are shared. The “VLIO” interface has separate read and write lines, but the address and data lines are multiplexed. Almost all of the 8-bit UARTs are compatible with the industry-standard 16550 UARTs, hence, they can use the standard serial port drivers in almost all operating systems.

The 2-channel 8-bit UART family integrates 2 UARTs into a single package and further simplifies the hardware design by eliminating redundant external components. In the “Intel” mode, there is a chip select and interrupt pin per channel. In the “Motorola” mode, there is only 1 chip select and 1 interrupt pin. Most UARTs in this family are software compatible with the industry standard 16550 UART, so they can be used with the standard serial port drivers in most operating systems. Some products in this family also have a parallel port (ST16C452/452PS/552/552A). The parallel ports will work with standard parallel port drivers.

The 4-channel and 8-channel product families integrate 4 and 8 UARTs into a single package. In addition, the XR16L784 and XR16xx98 families also support a single chip select and single interrupt pin in both the “Intel” and “Motorola” mode to simplify the hardware design. These devices also have a global interrupt status register so the software can quickly determine which UART generated the interrupt without having to check the status of all of the individual UART channels. Almost all of these UARTs are based on the industry-standard 16550 UART, and are therefore compatible with standard serial port drivers. However, some driver customization may be required. Assistance for customizing software drivers is available from Exar’s UART technical support team.


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