Rev. 0.2 5/14 Copyright © 2014 by Silicon Laboratories AN187

AN187

CONNECTING THE SI3050/19 TO THE W&G PCM-4

1. Overview

The Si3050 evaluation board can easily be connectedto many PCM bus sources. One industry standard forPCM testing is the Wandel and Goltermann modelPCM-4. The PCM-4 tests telephone linecard voiceparametrics in the two-wire and PCM domains. Thisdocument describes the connections from a typicalPCM-4 to the Si3050 evaluation board. The PCM-4should be an option “E” which generates a 2.048 MHzPCM clock.

1.1. Typical Digital ConfigurationThe PCM-4’s typical configuration has the PCM clockand transmit and receive connections on the front panel.

The PCM frame sync (8 kHz) is accessible from the rearof the PCM-4. The BNC cable connections to theSi3050 evaluation board should be made as follows:

Connect the PCM-4 Frame Trigger (61) to the PCM-4 Ext. Frame (63) with a BNC”T”. See Figure 1.

Connect the PCM-4 Ext. Frame (63) BNC”T” to the Si3050 evaluation board FSYNC. See Figure 1.

Connect the PCM-4 RX Signal (20) to the Si3050 evaluation board DTX. See Figure 2.

Connect the PCM-4 TX Signal (21) to the Si3050 evaluation board DRX. See Figure 2.

Connect the PCM-4 TX Clock (22) to the Si3050 evaluation board PCLK. See Figure 2.

Figure 1. W&G PCM-4 Rear Panel

AN187

2 Rev. 0.2

Figure 2. W&G PCM-4 Signal and Clock Connections

Figure 3. PCM-4 Front Panel

AN187

Rev. 0.2 3

1.2. Alternative Configuration SettingsThe PCM-4 also has configuration settings that allowPCM connection to a variety of PCM environments. TheSi3050 evaluation board requires three modifications tothe default configuration settings:

General Parameters—2.14

General Parameters—3.13

General Parameters—4.13

For -law add the following:

General Parameters—7.12

General Parameters—7.22

1.3. Typical Analog ConfigurationThe Si3050 requires a dc current source (loop current)to operate in the offhook state. The PCM-4 does notprovide this loop current so it must be provided throughan external source as shown in Figure 4. This sourceshould provide loop current between 20 mA and120 mA. This external source must be isolated from thePCM-4 so it will not affect the audio measurementsbeing made. Two large inductors (> 3 H) should beused to isolate the ac impedance of the current source.This external current may damage the PCM-4.

Because of this, the current must be blocked from thePCM-4. Two large capacitors (> 10 F) should be usedto block the dc current while not adversely affecting thevoiceband measurements of the PCM-4. Wandel andGoltermann provides an analog dc blocking interface(PCMZ-4) that may be used instead of these blockingcapacitors.

1.4. PCM TransfersThe PCM-4 is now ready for A-D, D-A and D-D PCMtransfers at time slot 0 (the default timeslot for theSi3050). Proceed by performing the following steps:

1. Apply power to the Si3050EVB.

2. Start Silicon Labs Voice GUI.

3. Write the following registers of the Si3050:

a.Register 33 to 0x20h (A-law companding)

b.Register 31 to 0xA0h (set full scale mode)

c.Register 26 to 0xC0h (set DC termination)

d.Register 16 to 0x10h (set digital filter to IIR)

e.Register 6 to 0x00h (enable the IsoCAP link)

f.Register 5 to 0x01h (take DAA offhook)

8. Perform audio tests.

Figure 4. Typical Configuration

To PCM-4 DigitalInterface

Si3050/19

DC CurrentSource

AC BlockingInductors (>3 H)

To PCM4 AnalogInterface

DC BlockingCapacitors (>10 F)

DisclaimerSilicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products must not be used within any Life Support System without the specific written consent of Silicon Laboratories. A "Life Support System" is any product or system intended to support or sustain life and/or health, which, if it fails, can be reasonably expected to result in significant personal injury or death. Silicon Laboratories products are generally not intended for military applications. Silicon Laboratories products shall under no circumstances be used in weapons of mass destruction including (but not limited to) nuclear, biological or chemical weapons, or missiles capable of delivering such weapons.

Trademark InformationSilicon Laboratories Inc., Silicon Laboratories, Silicon Labs, SiLabs and the Silicon Labs logo, CMEMS®, EFM, EFM32, EFR, Energy Micro, Energy Micro logo and combinations thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZMac®, EZRadio®, EZRadioPRO®, DSPLL®, ISOmodem ®, Precision32®, ProSLIC®, SiPHY®, USBXpress® and others are trademarks or registered trademarks of Silicon Laboratories Inc. ARM, CORTEX, Cortex-M3 and THUMB are trademarks or registered trademarks of ARM Holdings. Keil is a registered trademark of ARM Limited. All other products or brand names mentioned herein are trademarks of their respective holders.

http://www.silabs.com

Silicon Laboratories Inc.400 West Cesar ChavezAustin, TX 78701USA

Smart.Connected.Energy-Friendly

Productswww.silabs.com/products

Qualitywww.silabs.com/quality

Support and Communitycommunity.silabs.com