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IDT82P2281
SINGLE T1/E1/J1 LONG HAUL / SHORT HAUL TRANSCEIVER
Functional Description
54
October 7, 2003
The RSCK is gapped during the F-bit if the FBITGAP bit is set to ‘1’.
The RSCK is also gapped during the channels or the Bit 8 duration by
selecting the G56K & GAP bits in the Receive Payload Control. The data
in the corresponding gapped duration is a don't care condition.
3.17.1.2
Receive Clock Slave Mode
In the Receive Clock Slave mode, the system data rate can be
1.544 Mb/s or 2.048 Mb/s. If the system data rate is 1.544 Mb/s, it works
in T1/J1 mode. If the system data rate is 2.048 Mb/s, the received data
stream (1.544 Mb/s) should be mapped to the same rate as the system
side, that is, to work in T1/J1 mode E1 rate. Three kinds of schemes are
provided by selecting the MAP[1:0] bits:
1. T1/J1 Mode E1 Rate per G.802 (refer to Figure 17): Channel 1 to
Channel 15 of Frame N from the device are converted into TS1 to TS15
of Frame N on the system side; Channel 16 to Channel 24 of Frame N
from the device are converted into TS17 to TS25 of Frame N on the sys-
tem side. The F-bit of Frame N from the device is converted into the first
bit of TS26 of Frame (N-1) on the system side. TS0, TS16, TS27~TS31
and the other 7 bits in TS26 on the system side are all filled with ‘0’s and
they are meaningless.
2. T1/J1 Mode E1 Rate per One Filler Every Four CHs (refer to
Figure 18): One dummy byte is inserted on the system side before 3
bytes of Frame N from the device are converted. This process repeats 8
times and the conversion of Frame N of 1.544 Mb/s data rate to 2.048
Mb/s data rate is completed. However, the F-bit of Frame N of the 1.544
Mb/s data rate is inserted as the 8th bit of Frame N of the 2.048 Mb/s
data rate. The dummy bytes are filled with all ‘0’s and they are meaning-
less.
3. T1/J1 Mode E1 Rate per Continuous CHs (refer to Figure 19):
Channel 1 to Channel 24 of Frame N from the device are converted into
TS1 to TS24 of Frame N on the system side. The F-bit of Frame N from
the device is converted into the 8th bit of Frame N on the system side.
The first 7 bits and TS25 to TS31 on the system side are all filled with
‘0’s and they are meaningless.
Figure 17. T1/J1 To E1 Format Mapping - G.802 Mode
Figure 18. T1/J1 To E1 Format Mapping - One Filler Every Four Channels Mode
1.544
Mb/s
2.048
Mb/s
CH1
CH2
CH14
F
CH15
CH16
CH17
CH23
CH24
CH1
CH2
F
CH23
TS0
TS2
TS1
TS14
TS15
TS16
TS17
TS18
TS24
TS25
TS26 TS27~TS31
TS0
TS1
the 1st bit
filler
filler
filler
filler
filler
1.544
Mb/s
2.048
Mb/s
CH1
CH2
CH3
F
CH4
CH5
CH6
CH22
CH23
CH24
CH1
F
CH2
TS0
TS2
TS1
TS4
TS5
TS6
TS7
TS8
TS28 TS29 TS30 TS31
TS1
TS0
the 8th bit
CH7
TS3
TS9
the 8th bit
filler
filler
filler
filler
filler