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Using SI_SCOPE In Async Mode With USB-RS232 ConvertersSI_SCOPE supports utilizing USB to RS232 converter hardware for bidirectional Async mode capture. Please note that when configured this way SI_SCOPE has to utilize the drivers supplied by the hardware manufacturer in order to see the USB device. This means that SI_SCOPE will not be able to capture and time stamp data at the interrupt level. As a result it is possible that the time stamping between two characters may appear as if the characters were received at the same time or the sequence of events may appear out of order from what actually happened. The source of an event will always be correct but it is possible that the first byte of a response packet may appear to have been captured before the last byte of a command packet if the idle time between the response and command is less than the USB drivers poll time. For most USB devices we have found the idle time to be from 1 to 5 milliseconds based on tests performed in our lab with different USB converter devices. For most users this is not an issue and the convenience and low cost of the USB hardware makes this an attractive option. However if you need accurate inter-character time stamping or you are trying to reverse engineer an unknown protocol then it is recommended that you use a PCI or PCMCIA card instead. When configured with a PCI or PCMCIA card SI_SCOPE will load its own driver and the received data is recorded and time stamped at the interrupt level. Click here to go back to the SI_SCOPE information page.
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For more information please email us at: info@rs232-serial-communications.com or call us at 845-566-1919Copyright © 2008
Software Innovations, Inc.
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