DS2148 Dallas Semiconducotr, DS2148 Datasheet - Page 44

• Manufacturer Part Number: DS2148
• Description: 5V E1/T1/J1 Line Interface
• Manufacturer: Dallas Semiconducotr

RDNCD2 (10H): RECEIVE DOWN CODE DEFINITION REGISTER 2
8.2
8.2.1 Remote Loopback (RLB)
the clock/data recovery state machine will be looped back to the transmit path passing through the jitter
attenuator if it is enabled. The data at the RPOS and RNEG pins will be valid while data presented at
TPOS and TNEG will be ignored (Figure 3-1).
If the Automatic Remote Loop Back Enable (CCR6.5) is set to a one, the DS2148 will automatically go
into remote loop back when it detects the loop up code programmed in the Receive Up Code Definition
Registers (RUPCD1 and RUPCD2) for a minimum of 5 seconds. When the DS2148 detects the loop
down code programmed in the Receive Loop Down Code Definition registers (RDNCD1 and RDNCD2)
for a minimum of 5 seconds, the DS2148 will come out of remote loop back. Setting ARLBE to a zero
also can disable the ARLB.
8.2.2 Local Loopback (LLB)
When LLB (CCR6.7) is set to a one, the DS2148 is placed into local loopback. In this loopback, data on
the transmit-side will continue to be transmitted as normal. TCLK and TPOS/TNEG will pass through the
jitter attenuator (if enabled) and be output at RCLK and RPOS/RNEG. Incoming data from the line at
RTIP and RRING will be ignored. If Transmit Unframed All Ones (CCR3.7) is set to a one while in LLB,
TTIP and TRING will transmit all ones while TCLK and TPOS/TNEG will be looped back to RCLK and
RPOS/RNEG (Figure 3-1).
When RLB (CCR6.6) is enabled, the DS2148 is placed into remote loopback. In this loopback, data from
(MSB)
C15
SYMBOL
C15
C14
C13
C12
C11
C10
Loopbacks
C9
C8
C14
POSITION
RDNCD2.7
RDNCD2.6
RDNCD2.5
RDNCD2.4
RDNCD2.3
RDNCD2.2
RDNCD2.1
RDNCD2.0
C13
DESCRIPTION
Receive Down Code Definition Bit 15
Receive Down Code Definition Bit 14
Receive Down Code Definition Bit 13
Receive Down Code Definition Bit 12
Receive Down Code Definition Bit 11
Receive Down Code Definition Bit 10
Receive Down Code Definition Bit 9
Receive Down Code Definition Bit 8
C12
44 of 75
C11
C10
C9
(LSB)
C8