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DS3171/DS3172/DS3173/DS3174
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Table 10-24. RCLKOn/RGCLKn Output Pin Functions
FM[2:0]
RCLKS
Pin function
Gap source
0XX (FSCT)
0
RGCLKn
RDENn
0XX (FSCT)
1
RCLKOn
none
1XX (FBM)
X
RCLKOn
none
10.5.9 Framing Modes
The framing modes are selected independently of the line interface modes using the
PORT.CR2
.
FM[2:0] control
bits. Different blocks are used in different framing modes. The bit error test (BERT) function can be enabled in any
mode. The LIU, JA and line encoder/decoder blocks are selected by the line mode (LM[2:0]) code.
Table 10-25. Framing Mode Select Bits FM[2:0]
FM[2:0] Description
Line
Code
Figure
000
DS3 C-bit Framed
B3ZS/AMI/UNI
001
DS3 M13 Framed
B3ZS/AMI/UNI
010
E3 G.751 Framed
HDB3/AMI/UNI
011
E3 G.832 Framed
HDB3/AMI/UNI
100
DS3 Rate Clear Channel
B3ZS/AMI/UNI
11X
E3 Rate Clear Channel
HDB3/AMI/UNI
10.5.10 Line Interface Modes
The line interface modes can be selected semi-independently of the framing modes using the
PORT.CR2
.
LM[2:0]
control bits. The major blocks controlled are the transmit LIU (TX LIU), receive LIU (RX LIU), jitter attenuator (JA)
and the line encoder/decoder. The line encoder/decoder is used for B3ZS, HDB3 and AMI line interface encoding
modes. The line encoder-decoder block is not used for line encoding or decoding in the UNI mode but the BPV
counter in it can be used to count external pulses on the RNEGn / RCLVn pin. The jitter attenuator (JA) can be off
(OFF) or put in either the transmit (TX) or receive (RX) path with the TX LIU or RX LIU. Both TX LIU and RX LIU
can be enabled (ON) or disabled (OFF).
The “Analog Loop Back” (ALB) is available when the LIU is enabled or disabled. It is an actual loop back of the
analog positive and negative pulses from the TX LIU to the RX LIU when the LIU is enabled. If the LIU is disabled,
it is a digital loop back of the TLCLK, TPOS, TNEG signals to the RLCLK, RPOS and RNEG signals.
When the line is configured for B3ZS/HDB3/AMI line codes, the line codes are determined by the framing mode
and the TZCDS and RZCDS bits control the AMI line mode selection bits in the line encoder/decoder blocks. The
DS3 modes select the B3ZS line coding, the E3 modes select the HDB3 line codes. Refer to
configuration.