
QuadFALC
TM
PEF 22554 E
Functional Description E1
Data Sheet
166
Rev. 1.2, 2006-01-26
4.7.3
Payload Loop-Back (E1)
To perform an effective circuit test a payload loop is implemented.
The payload loop-back is activated by setting FMR2.PLB (FMR2_E).
During activated payload loop-back the data stream is looped from the receiver section back to transmitter section.
The looped data passes the complete receiver including the wander and jitter compensation in the receive elastic
buffer and is output on pin RDO. Instead of the data an AIS signal (FMR2.SAIS) can be sent to the system
interface.
The framing bits, CRC4 and spare bits are not looped, if XSP.TT0 = 0 (XSP_E). They are generated by the
QuadFALC
TM transmitter. If the PLB is enabled the transmitter and the data on pins XL1/2 or XDOP/XDON are
clocked with SCLKR instead of SCLKX. If XSP.TT0 = 1 the received time slot 0 is sent back transparently to the
line interface. Data on the following pins is ignored: XDI, XSIG, SCLKX, SYPX and XMFS. All the received data
is processed normally.
Figure 61
Payload Loop (E1)
4.7.4
Local Loop (E1)
The local loop-back is activated by
The control bit LIM0.LL (LIM0_E).
After detection of the appropriate In-band loop code, if enabled by ALS.SILS, see Chapter 4.5.6.
The local loop-back mode disconnects the receive lines RL1/2 or RDIP/RDIN from the receiver. Instead of the
signals coming from the line the data provided by the system interface is routed through the analog receiver back
to the system interface. However, the bit stream is transmitted undisturbedly on the line. However, an AIS to the
distant end can be enabled by setting FMR1.XAIS = 1 without influencing the data looped back to the system
interface.
Note that enabling the local loop usually invokes an out-of-frame error until the receiver resynchronizes to the new
framing. The serial codes for transmitter and receiver have to be identical.
ITS09748
Clock +
Data
Rec.
Framer
Elast.
Store
Trans.
Framer
RDO
XDI
RCLK
RL1
RL2
XL1
XL2
Recovery
SCLKX
SCLKR
MUX
AIS-GEN
Elast.
Store