Maxim DS33Z41 Especificações descarregar pdf (Página 19)

In Maxim TDMoP devices, for an ARP request, all the fields are filled in except the target hardware address. When a

system receives an ARP request, it fills in its hardware address, swaps the two sender addresses with the two target

addresses, sets the 'operation' field to 2, and sends the reply.

Q7. What are the ground considerations when using an Ethernet PHY interface?

A7. With any electrical system, choosing the appropriate grounding scheme is crucial for proper operation. There are

three main types of electrical grounds: earth ground, signal ground, and chassis ground. Although similar in function,

each of the grounds is used differently. Secondly, the grounds may also be at a different electrical potential with respect

to each other.

There are several reasons why a designer may choose to have more than one ground in a particular design. The main

reasons deal with noise reduction and signal isolation. When using an Ethernet PHY, it is important to isolate the signals

from the CAT-5 Ethernet cable to the reset of the system. This is done by using specialized Ethernet magnetics with each

side of the transformer referenced to the appropriate ground. Please notice the two separate grounds in Figure 3.

Figure 3. Typical Ethernet PHY connection.

Q8. Can you define the Stratum levels for TDMoP devices?

A8. A Stratum 1 clock is defined as a completely autonomous source of timing, which has no other input other than,

perhaps, a yearly calibration. It has an accuracy of 1.0 × 10

-11

. A Stratum 1 clock may control Stratum 2, 3E, 3, 4E, or 4

clocks. A Stratum 2 clock may drive Stratum 2, 3E, 3, 4E, or 4 clocks. A Stratum 3E clock may drive Stratum 3E, 3, 4E,

or 4 clocks.

Stratum 2 tracks an input under normal operating conditions, and holds to the last best estimate of the input reference

frequency during impaired operating conditions. It has an accuracy of 1.6 × 10

-8

Stratum 3 is defined as a clock system that tracks an input as in Stratum 2, but over a wider range. It has an accuracy of

4.6 × 10

-6

. A Stratum 3 clock may drive Stratum 3 or 4 clocks. A Stratum 4 clock is not recommended as a source of

timing for any other clock system.

Stratum 3E is a relative new standard created as a result of SONET equipment requirements. It has an accuracy of 1.0 ×

-6

Stratum 4 is defined as a clock system that tracks an input as in Stratum 2 or 3. It has an accuracy of 3.2 × 10

-5

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Maxim DS33Z41 Especificações Página 19