Rainbow Electronics DS3170 - Manual (Page 77)

DS3170 DS3/E3 Single-Chip Transceiver
77 of 233
Table 9-23. RSOFO/RDEN Output Pin Functions
FM[2:0]
PORT.CR2
RSOFOS
PORT.CR3
PIN
FUNCTION
0XX (FRM) 0 RDEN
0XX (FRM) 1 RSOFO
1XX (UFRM) X High
Table 9-24. RCLKO/RGCLK Output Pin Functions
FM[2:0]
PORT.CR2
RCLKS
PORT.CR3
PIN
FUNCTION
GAP SOURCE
0XX (FRM) 0 RGCLK RDEN
0XX (FRM) 1 RCLKO none
1XX (UFRM) X RCLKO none
9.5.9 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 9-25. Framing Mode Select Bits FM[2:0]
FM[2:0] DESCRIPTION LINE CODE FIGURE
0 00 DS3 C-bit Framed B3ZS/AMI/UNI Figure 6-1
0 01 DS3 M23 Framed B3ZS/AMI/UNI Figure 6-1
0 10 E3 G.751 Famed HDB3/AMI/UNI Figure 6-1
0 11 E3 G.832 Framed HDB3/AMI/UNI Figure 6-1
1 00 DS3 Unframed B3ZS/AMI/UNI Figure 6-2
1 01 Undefined ---
1 10 E3 Unframed HDB3/AMI/UNI Figure 6-2
1 11 Undefined ---
9.5.10 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 RNEG / RCLV 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 AMI line mode selection is controlled by the TZCDS and RZCDS 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
Table 9-26 for
configuration.