Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 250)

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10.3. Board Test
The modem and DAA chips come from Silicon Laboratories 100% functionally tested on automatic test equipment
to guarantee compliance with the published chip specifications. The functionality of a finished product containing
an ISOmodem chipset depends not only on the functionality of the modem chipset after assembly but also on
discrete components and product-related software. Finished product test requirements and procedures depend on
the manufacturer and on the product. Consequently, no universal final test procedure can be defined.
Testing the modem in a finished product is done for several reasons. First, it is important to be sure the modem
chipset and peripheral components were installed correctly during assembly and were not damaged. Second, it is
necessary to be sure the correct component values were installed and that there are no manufacturing problems,
such as solder bridges, cold solder joints, or missing components.
Functional testing can be used to test special features, such as intrusion detection, Caller ID, and overcurrent
detection. An intrusion can be simulated by placing a 1 k
 resistor across Tip and Ring through a relay. Caller ID
testing requires special test equipment, such as the Rochelle 3500 or Advent AI-150.
Many manufacturers choose to use built-in self-test features, such as the &T3 Loopback test described above.
Others do a complete functional test of the modem by originating and answering a call and successfully passing a
data file in each direction. This process tests the modem and line-side chip functionality, the associated external
components, and the software controlling the modem. This test can be done with a modem under test (MUT) and a
known-good reference modem, or between two modems under test. Testing two modems under test at once
reduces test and setup times. Modem operational testing is time consuming and adds to product cost. It is up to the
manufacturer to determine whether operational testing is warranted.
Analog modems (Bell 103 through V.34) can be tested by connecting the modems through a telephone line
simulator, such as Teltone TLS-3. A call can be placed or received in either direction at the speed set in the
modems. A test script must be written for a computer to control the dialing, monitor the call progress, send a file,
and compare the received and sent file. Figure 46 illustrates this test configuration.
Figure 46. Bell 103–V.34 Modem Functional Test Connection
Teltone TLS 3
Modem Under
Test
Reference Modem
Test
Computer