Maxim DS33Z41 Especificações descarregar pdf (Página 6)

● American National Standards Institute - ANSI (www.ansi.org)

● European Telecommunications Standards Institute - ETSI (www.etsi.org)

● International Telecommunication Union - ITU (www.itu.int)

● Telecommunication Technology Committee - TTC (www.ttc.or.jp)

● Telecommunications Industry Association - TIA (www.tiaonline.org)

● Telcordia Technologies, Inc. - Telcordia (www.telcordia.com)

● Underwriters Laboratories, Inc. - UL (www.ul.com), UL Europe (www.ul-europe.com)

Q13. When the boundary scan is not used, what will be the pin conditions for the JTAG test

access pins?

A13. For the boundary scan, each device uses five pins. These are the JTCLK, JTDI, JTMS, JTRST, and JTDO pins. When

the boundary scan is not used, these pins must have a steady value. For JTCLK, it should be pulled high. JTDI and JTMS

should be unconnected or high, because they both have an internal 10kΩ pullup resistor. JTRST also has a 10kΩ pullup

resistor, and it asynchronously resets the test access port when the pin is toggled from low to high. It needs to be held

high or low when the boundary scan is not used. JTDO should be left unconnected.

Q14. For a universal T1/E1 interface on the customer side, do T1/E1 service providers expect

customer equipment to provide a connection between the Tx and Rx pairs through the

transformer center taps? Or, can the T1/E1 service provider ignore this connection and leave it

out of the design?

A14. The need for transformer center tap connection between the Tx and Rx pairs depends on the design and, most of

the time, it is recommended that this connection is ignored. Most T1 service providers do not expect there to be a

connection between the transformer center taps of Rx and Tx pairs.

Please refer to application note 324, "

T1/E1 Network Interface Design," for more information regarding design of a

telecommunications network interface circuit using Maxim line interface units (LIUs) or single-chip transceivers (SCTs).

For an E1 network, hardware board designers cannot connect the center taps of Rx and Tx at any time. For a T1 network,

the designers need to make sure that they are using 5V parts if they want to connect the center taps of Rx and Tx sides

of the transformer. With 3.3V parts, however, they cannot connect the center taps.

If the customer is planning to create a new design with DS2155/DS2156, then it is recommended to refer to Figures 4

and 5 of application note 324. However, if the customer is using the DS2151 or DS2153, then it is recommended to refer

to Figures 2 and 3 instead.

Q15. What is the difference between channelized and unchannelized T1?

A15. Channelized T1 splits into 24 voice-grade channels, with each running at 64kbps. If you have a need for numerous

local phones, it is much cheaper to get them delivered on T1 channels than as individual phone lines. Channelized T1 is

developed and optimized for uncompressed voice communications. The channelized approach is required for access to the

tradition PSTN.

Unchannelized T1 provides you with 1.536Mbps (minus a framing bit), which you can split up anyway you choose. It is

ideal for most data-communications applications, as well as compressed voice, video, and IP telephony. For example, you

can split a leased T1 into 12 voice-grade channels to support 12 voice conversations, and then use the remaining

768kbps for either reasonably high-speed access to the Internet or for videoconferencing with your distant office. You can

also compress voice to run at speeds of perhaps 8kbps or less by using IP telephone techniques and, therefore, put many

more voice calls over a single T1 pipe.

Q16. Can I modify the codes of Maxim telecommunication drivers?

A16. No. Maxim has the license of the driver that allows us to provide the driver code to the customers, but it does not

change the ownership of the driver nor put it under the GNU licensing schemes. The customer can extend the driver

through the macros or other recommended function commands.

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