Datasheet

____________________________________________________ DS34T101, DS34T102, DS34T104, DS34T108
126 of 366
Register Name Description Functions Page
TDS0M Transmit DS0 Monitor Register
Tx channel data
301
RDS0SEL Rx DS0 Monitor Select Register
Rx channel to be monitored
228
RDS0M Rx DS0 Monitor Register
Rx monitored data
237
In the transmit direction TCM[4:0] field in TDS0SEL
specifies the channel to be monitored. In the Rx direction, the
RCM[4:0] field in RDS0SEL spe
cifies the channel to be monitored. Data from the specified channel is available to
be read from the TDS0M or
RDS0M register respectively.
10.11.10 Framer and Payload Loopbacks
Framer loopback (enabled when RCR3.FLB=1) is useful in testing and debugging applications. In FLB, the full E1
or T1 data stream is looped from the line (LIU) side of the transmit formatter to line side of the Rx framer. When
FLB is enabled, the following occur:
1. (T1 mode) an unframed all-ones code is output from the transmit formatter toward the LIU
(E1 mode) normal data is output from the transmit formatter toward the LIU
2. Data from the LIU or RDATF pin is ignored by the Rx framer
3. All Rx framer signals have timing synchronous with TCLK instead of RCLK.
In payload loopback (enabled when RCR3.PLB=1
), the 192 bits of payload in each T1 frame or the 248 bits of
payload in each E1 frame are looped back (with BPVs corrected) from the Rx framer to transmit formatter. In this
mode the Rx frame alignment is automatically provided to the transmit formatter, such that the transmit frame
alignment is locked to the Rx frame alignment (i.e., TSYNC is sourced from RSYNC). The T1 F-bits and E1 FAS
and NFAS bytes are not looped back. Instead they are reinserted by the formatter (i.e., the formatter modifies the
payload as if it were input at TSER).
When PLB is enabled, the following occurs:
1. Data from the transmit formatter toward the LIU is synchronous with RCLK instead of TCLK
2. All of the Rx framer signals continue to operate normally
3. Data at the TSER and TSIG inputs to the transmit formatter is ignored
Table 10-55. Registers Related to Framer and Payload Loopbacks
Register Field Description Functions Page
RCR3.FLB Framer Loopback Tx formatter output looped back to Rx framer input 248
RCR3.PLB Payload Loopback Rx framer payload looped back to Tx formatter input 248
10.11.11 Per-Channel Loopback
The per-channel loopback registers (PCL) determine, in the transmit formatter, which channels (if any) from TSER
should be replaced with data from the same channel of the data stream being received by the Rx framer. For this
loopback to work correctly, the transmit and Rx clocks and frame syncs must be synchronized. One method to
accomplish this would be to tie RCLK to TCLK and RFSYNC to TSYNC with TSYNC configured as an input
(TIOCR.TSIO=0). There are no restrictions on which channels can be looped back or how many channels can be
looped back.
Each bit in the PCL
registers represents a DS0 channel transmit formatter’s data stream. When a bit is set to one,
data from the corresponding Rx channel replaces the data from TSER for that channel.
10.11.12 Per-Channel Idle Code Insertion
Channel data can be replaced by an idle code on a per-channel basis in both the transmit and Rx directions. The
32 Rx idle definition registers (RIDR) specify the
8-bit idle code for each channel. The Rx channel idle code enable
registers (RCICE) a
re used to enable idle code insertion on a per-channel basis. Similarly the 32 TIDR registers