Asynchronous data transfer
The term asynchronous is usually used to describe communications in which data can be transmitted intermittently rather than in a steady stream. For example, a telephone conversation is asynchronous because both parties can talk whenever they like. If the communication were synchronous, each party would be required to wait a specified interval before speaking. The difficulty with asynchronous communications is that the receiver must have a way to distinguish between valid data and noise. In computer communications, this is usually accomplished through a special start bit and stop bit at the beginning and end of each piece of data. For this reason, asynchronous communication is sometimes called start-stop transmission.
RS232
RS-232 (Recommended standard-232) is a standard interface approved by the Electronic Industries Association (EIA) for connecting serial devices. In other words, RS-232 is a longestablished standard that describes the physical interface and protocol for relatively low-speed serial data communication between computers and related devices.
An industry trade group, the Electronic Industries Association (EIA), defined it originally for teletypewriter devices. In 1987, the EIA released a new version of the standard and changed the name to EIA-232-D. Many people, however, still refer to the standard as RS-232C, or just RS-232.
RS-232 is the interface that your computer uses to talk to and exchange data with your modem and other serial devices. The serial ports on most computers use a subset of the RS- 232C standard.
USB TO RS232
STEP’S Loop-back test
If you experience any communication problems when using a USB to Serial RS232 adapter then you can make a loop-back test to find out if the adapter is properly working; this way you might be able to determine if the problem is caused by the adapter, your equipment or the drivers.
Confirming successful COM port installation.
In order to make a loop-back test you first need to make sure that the drivers and COM port has
been successfully installed.
1. With the USB Serial drivers installed, connect your USB serial adapter to your computer’s USBport.
2. Check in Windows Device Manager (Start -> Control Panel -> System -> Hardware tab ->Device Manager) under Ports (COM & LTP) if the COM port has been successfully created:
If the
If the COM port is not listed in the Device Manager it has not been successfully created and you need to determine the cause. This could be due to incorrect drivers, conflicting drivers if you have other USB serial drivers installed, or simply an unsuccessful driver installation. A solution could be to uninstall all current USB serial drivers, reboot and re-install the most recent drivers again.
Notice: a reboot is highly recommended after each driver un-installation/installation.
2. The main driver screen will open where the adapter’s Device Status in
3. Then HyperTerminal OPEN and create NEWConnection
4. Under the Port Settings tab you will find the Advanced settings button:
THEN FINESH LOOP BACK TEST(HYPER-TERMINAL DATA WITHOUT ERROR RECIVE)
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