Article ID: 184068 - View products that this article applies to.
This article was previously published under Q184068
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This article describes the differences between software modems and standard modems.
Traditionally, modems have performed the following basic functions:
The design of these modems differs greatly from one manufacturer or model to the next. For example, some are equipped with a DSP) and rely on software for other functions, while others may rely almost entirely on emulation.
The common factor for all software modems is a reliance on software emulation of the UART chip. This is the chip that the operating system communicates with to send or receive information across the serial or com ports. When the proper driver is loaded, calls to the UART chip are redirected to the emulation software. The program believes that it is communicating with the UART chip.
NOTE: If there is no MS-DOS driver loaded for your software modem, you are unable to use the modem in MS-DOS mode. An MS-DOS program running in Windows (also known as a virtual machine or VM) can use the modem if it is written to take advantage of the Windows protected-mode drivers.
It may be difficult to determine if you have a software modem since not all software modems are called software modems. To determine if you have a software modem, view your modem documentation or contact your hardware vendor.
NOTE: Echoing AT commands to a com port does not work with a software modem since MS-DOS expects to communicate with the UART chip directly.
Software modems may also be referred to as controller-less modems, Host Signal Processing (HSP) modems, or winmodems. Two popular chipsets for software modems are the RPI and the HSM chipsets.
Article ID: 184068 - Last Review: January 22, 2007 - Revision: 2.1
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