XRT86VL38
PRELIMINARY
xr
OCTAL T1/E1/J1 FRAMER/LIU COMBO
REV. P1.0.6
315
4.10
Overhead Interface
The Overhead interface provides an option for inserting the datalink bits into the transmit PCM data or
extracting the datalink bits from the receive PCM data. By default, the datalink information is processed to and
from the PCM data directly. On the transmit path, the overhead clock is automatically provided as a clock
reference to externally time the datalink bits. The user should provide data on the rising edge of the TxOHclk
so that the framer can sample the datalink bits on the falling edge. On the receive path, the datalink bits are
updated on the rising edge of the RxOHclk output pin. In T1 ESF mode, a datalink bit occurs every other
frame. Therefore, the default overhead interface is operating at 4kbps. In E1 mode, the datalink bits are
located in the first time slot of each Non-FAS frame. Figure 24 is a simplified block diagram of the Overhead
Interface. Figure 25 is a simplified diagram for the T1 external overhead datalink bus. Figure 26 is a simplified
diagram for the E1 external overhead datalink bus.
F
IGURE
23. SF / SLC-96
OR
4-
CODE
S
IGNALING
IN
ESF / CAS E
XTERNAL
S
IGNALING
B
US
F
IGURE
24. T1/E1 O
VERHEAD
I
NTERFACE
TxSYNC
TxMSYNC
TxSERclk
TxCHN0/TxSIG
TxSER
F
B
A
TS 1
B
A
B
A
TS 2
TS 3
Datalink Bits
PCM Data
Tx LIU
Rx LIU
Datalink Bits
PCM Data
Transmit Direction
Receive Direction
TxSER
TxOH
RxSER
RxOH
Physical
Interface
TxOHclk
RxOHclk