What Sealevel asynchronous serial adapters support 9-bit protocols?

  Any Sealevel asynchronous serial adapter that includes a 16C950 UART or 16C954 quad-port UART natively supports 9-bit framing in hardware. USB serial adapters use a different chipset and are not capable of 9-bit data framing. Other Sealevel serial adapters can be upgraded with a 16C950 or 16C954 UART for a nominal charge. Call for […]

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When should I use the RFC 2217 mode of my SeaLINK Ethernet serial server?

  RFC 2217 is a popular protocol for accessing serial ports over a network. A server that uses RFC 2217 allows its serial port to be controlled through the network by another device called an RFC 2217 client, which is often a computer. This RFC 2217 client can often use an application designed for an […]

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Where do I find a Linux driver for my Sealevel asynchronous serial adapter?

  Most Sealevel serial adapters use the serial drivers built into the Linux kernel. For USB and UART-based serial adapters, the Linux drivers may need additional information in order to provide access to the Sealevel serial device. For SeaLINK Ethernet serial servers, Sealevel offers a dedicated Linux driver.   To configure UART-based serial adapters, please […]

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Which Sealevel asynchronous serial adapters support isochronous communication mode?

  Most of our bus based adapters, including PCI Express, PCI, PCMCIA, PC/104 and ISA, can be used. The adapter must have a 16C950 UART installed and support the Ring Indicator (RI) signal. The 16C950 UART is necessary to allow the SeaCOM driver to put the adapter into isochronous mode. Ring Indicator accepts the external […]

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Why do I need optical isolation?

  Optical isolation improves the reliability of I/O applications in industrial, marine, mobile or similar environments, thus alleviating the problems caused by ground loops, electromagnetic interference (EMI) and surges. Duplicate ground references, referred to as ‘ground loops’, can occur when there is more than one path to ground between connected devices. Ground loops can also […]

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Why do I need to connect a ground line when using RS-422 or RS-485 communications?

  By connecting the ground wire, you avoid potential communication problems. Differential serial communications such as RS-422 and RS-485 use the ground as a reference. When there is no ground, the reference is basically floating. Communication failures can result if the floating reference causes the data line voltage to exceed the common mode range of […]

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Why does the mouse cursor randomly jump around when I connect a GPS to a Sealevel serial adapter?

  You are describing the “crazy mouse” syndrome, a common condition when Microsoft Windows receives NMEA 0183 data from a serial GPS device. The condition occurs when the GPS data is misinterpreted as mouse data by the Windows serial enumerator and will cause unwanted mouse cursor activity. It is most commonly encountered when connecting a […]

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Why don’t standard asynchronous serial adapters support 9-bit protocols?

  Applications that require 9-bit protocols are rare so the chips that support them are more expensive than standard 8-bit UARTs. Most 8-bit UARTs can simulate 9-bit protocols by setting the parity bit to mark or space. This was an easy solution on the 16C450 UART and other 8-bit UARTs without FIFO buffers. Modern 8-bit […]

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Why is my Ethernet serial connection timing out or not responding fast enough?

  By default, SeaLINK Ethernet serial servers use Nagle’s algorithm to reduce network traffic and increase serial data throughput, with the side effect of increasing latency. Both SeaLINK devices and the virtual COM port driver have settings to disable Nagle’s algorithm, also referred to as “nagling”. To reduce latency, disable Nagle’s algorithm in both the […]

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