W6691CD WINBOND [Winbond], W6691CD Datasheet - Page 40

• Manufacturer Part Number: W6691CD
• Description: ISDN S/T Interface Transceiver
• Manufacturer: WINBOND [Winbond]

7.2.8Test Functions
The W6691 provides loop and test functions as follows:
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Digital loop via DLP bit in D_MODE register: In the layer 2 block, the transmitted 2B+D data are
internally looped (from HDLC transmitter to HDLC receiver), and in the PCM ports, the
transmitted B channels are internally looped (from PCM inputs to PCM outputs). The clock
timings are generated internally and are independent of the S bus timing. This loop function is
used for test of PCM and higher layer functions, excluding layer 1. After hardware reset, W6691
will power down if S bus is not connected or if there is no signal on the S bus. In this case, the
C/I command ECK must be issued to power up the chip.
Analog loop via the C/I command EAL: The analog S interface transmitter is internally
connected to the S interface receiver. When the receiver has synchronized itself to the internal
INFO 3 signal, the message "Test Indication" or "Awake Test Indication" is delivered to the CIR
register. No signal is transmitted over the S interface.
In this mode, the S interface awake detector is enabled. Therefore if a level (INFO 2/ INFO 4) is
detected on the S interface, this will be reported by the "Awake Test Indication (ATI)" indication.
Remote loopback via RLP bit in D_MODE register: The digital 2B data received from the S
interface receiver is loopbacked to the S interface transmitter. The D channel is not looped.
When RLP is enabled, layer 1 D channel is connected to HDLC port and DLP cannot be
enabled.
Transmission of special test signals via layer 1 command:
* Send Single Pulses (SSP): To send isolated single pulses of alternating polarity, with pulse
width of one bit time, 250 us apart, with a repetition frequency of 2 kHz.
* Send Continuous Pulses (SCP): To send continuous pulses of alternating polarity, with pulse
width of bit time. The repetition frequency is 96 kHz.
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Preliminary W6691
Publication Release Date: Sep 2001
Revision 1.1