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Advance Data Sheet
T7633 Dual T1/E1 3.3 V Short-Haul Terminator
May 1998
52
Lucent Technologies Inc.
LIU-Framer Interface
(continued)
Interface Mode and Line Encoding
Single Rail
The default mode for the LIU-framer interface is single-rail, register LIU_REG3 bit 3 (DUAL) = 0 and register
FRM_PR8 bit 7 = 1, bit 6 = 1, and bit 5 = 0.
In the single-rail terminator mode (FRAMER = 1), the LIU bipolar encoder and decoder may be enabled by setting
register LIU_REG3 bit 2 (CODE) to 1. Signals passed on the internal LIU-framer interface are data (LIU_RPD and
TPD), clock (LIU_RLCK and TLCK), and received bipolar violations (LIU_RND/BPV). When LIU_RND/BPV = 1, the
BPV counter increments by one on the rising edge of LIU_RLCK.
In the single-rail framer mode (FRAMER = 0), external signals to and from the framer are data (RTIP_RPD, pin 11/
27 and TPD, pin 44/138), clock (RLCK, pin 47/135, and TLCK, pin 46/136), and received bipolar violations
(RRING_RND, pin 10/28). When RRING_RND = 1, the BPV counter increments by one on the rising edge of
RLCK. In this mode, TND (pin 45/137) is forced to the 0 state.
Dual Rail
Dual-rail LIU-framer interface mode is selected by setting LIU_REG3 bit 3 (DUAL) = 1 and by selecting one of the
dual-rail framer modes of FRM_PR8 bit 5—bit 7.
In the dual-rail terminator mode (FRAMER = 1), the framer bipolar encoder and decoder are enabled. Signals
passed on the internal LIU-framer interface are data (LIU_RPD, LIU_RND, TPD, and TND), and clock (LIU_RLCK
and TLCK). When bipolar violations are detected by the framer, the BPV counter increments by one on the rising
edge of LIU_RLCK.
In the dual-rail framer mode (FRAMER = 0), external signals to and from the framer are data (RTIP_RPD, pin 11/
27, RRING_RND, pin 10/28, TPD, pin 44/138, and TND, pin 45/137) and clock (RLCK, pin 47/135, and TLCK, pin
46/136). When bipolar violations are detected by the framer, the BPV counter increments by one on the rising edge
of RLCK.
DS1: Alternate Mark Inversion (AMI)
The default line code used for T1 is alternate mark inversion (AMI). The coding scheme represents a 1 with a pulse
(mark) on the positive or negative rail and a 0 with no pulse on either rail. This scheme is shown in Table 14.
Table 14. AMI Encoding
The T1 “ones density rule” states that:
In every 24 bits of information to be transmitted, there must be at least three pulses, and no more than 15
zeros may be transmitted consecutively [AT&T TR62411 (1988), ANSI T1.231 (1997)].
Receive ones density is monitored by the receive line interface as per T1M1.3/93-005, ITU G.775, or TR-TSY-
000009.
The receive framer indicates excessive zeros upon detecting any zero string length greater than fifteen contiguous
zeros (no pulses on either RPD or RND). Both excessive zeros and coding violations are indicated as bipolar viola-
tions.
Input Bit Stream
AMI Data
1011
–0+–
0000
0000
0111
0+–+
1010
–0+0