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Data Sheet
215
Rev. 1.2, 2006-01-26
QuadFALC
TM
PEF 22554 E
Functional Description T1/J1
Note that in the “N
× 56 kbit/s” mode the frame bit (defined here as the time slot 0) will not be used for PRBS, even
if it is selected by setting PRBSTS1.TS0. (In “N
× 56 kbit/s” mode PRBSTS1.TS0 is not valid.)
Note that the “N
× 56 kbit/s” mode is automatically a “framed” mode in T1/J1 because the time slot 0 is identical
to the frame bit.
Note that in “N
× 64 kbit/s” mode and enabling of all time slots by PRBSTS(1:4) all bits in the frame are used for
PRBS (that is an “unframed” mode).
The kind of PRBS patterns (polynomials) can be selected to be 2
11-1, 215-1, 220-1or 223-1 by the register bits
TPC0.PRP(1:0) and LCR1.LLBP, see Table 63. For definition of this polynomials see the Standards ITU-T O.150,
O.151. and TR62441. The polynomials 2
11-1 and 223-1 can be selected only if TPC0.PRM not 00b.
Transmission of PRBS pattern is enabled by register bit LCR1.XPRBS (LCR1_T). With the register bit LCR1.FLLB
switching between not inverted and inverted transmit pattern can be done.
The receive monitoring of PRBS patterns is enabled by register bit LCR1.EPRM. In general, depending on bit
LCR1.EPRM the source of the interrupt status bit ISR1.LLBSC changed, see register description. The type of
detected PRBS pattern in the receiver is shown in the status register bits PRBSSTA.PRS. Every change of the
bits PRS in PRBSSTA sets the interrupt bit ISR1.LLBSC if register bit LCR1.EPRM is set. No pattern is also
detected if signal “alarm simulation” is active.
The detection of all_zero or all_ones is done over 12, 16, 21 or 24 consecutive bits, depending on the selected
PRBS polynomial (2
11-1, 215-1, 220-1or 223-1 respectively). The detection of all_zero or all_ones is independent on
LCR1.FLLB.
The distinction between all-ones and all-zeros pattern is possible by combination of
The information about the first reached PRBS status after the PRBS monitor was enabled (“PRBS pattern
detected” or “inverted PRBS pattern detected”) with
The status information “all-zero pattern detected” or “all-ones pattern detected”
If an “all-one” or an “all-zero” pattern is detected by the PRBS monitor, the interrupt status bit ISR3.LLBSC is set
not only once, but is set permanent. To avoid that the LLBSC interrupt is issued permanent and the HOST micro
controller would permanent be occupied, the following proceeding is recommended:
After reading of the interrupt status bit ISR3.LLBSC , the appropriate interrupt routine should set the interrupt mask
bit IMR3.LLBSC to 1, after an “all-one” or an “all-zero” pattern was indicated, to avoid permanent interrupts
issued by the QuadFALC
TM. The PRBS status register bits PRBSSTA.PRS should be polled to detect changes in
the pattern, for example once per second, using the ISR3.SEC interrupt. In case PRBSSTA.PRS(2:1) is unequal
11
B, the interrupt mask bits should be cleared to return to normal operation.
Because every bit error in the PRBS sequence increments the bit error counter BEC, no special status information
like “PRBS detected with errors” is given here.
The time slot selection is related to the mapping used on the system interface.
Table 63
Supported PRBS Polynomials
TPC0.PRP(1:0)
TPC0.PRM
LCR1.LLBP
Kind of Polynomial Comment
00
01 or 11
X
2
11 -1
01
01 or 11
X
2
15 -1
10
01 or 11
X
2
20 -1
11
01 or 11
X
2
23 -1
XX
00
0
2
15 -1
SW compatible to
QuadFALC
XX
00
1
2
20 -1