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IDT82P2281
SINGLE T1/E1/J1 LONG HAUL / SHORT HAUL TRANSCEIVER
61
October 7, 2003
3.18.1.1.2
Besides all the common functions described in the Transmit Clock
Master mode, the special feature in this mode is that the TSCK is a
gapped 1.544 MHz clock (no clock signal during the selected channel).
The TSCK is gapped during the F-bit if the FBITGAP bit is set to ‘1’.
The TSCK is also gapped during the channels or the Bit 8 duration by
selecting the G56K & GAP bits in the Transmit Payload Control. The
data in the corresponding gapped duration is a Don't Care condition.
Transmit Clock Master Fractional T1/J1 Mode
3.18.1.2
Transmit Clock Slave Mode
In the Transmit 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 data stream to
be transmitted should be mapped to 1.544 Mb/s, 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 24): TS1 to TS15
of Frame N on the system side are converted into Channel 1 to Channel
15 of Frame N to the device; TS17 to TS25 of Frame N on the system
side are converted into Channel 16 to Channel 24 of Frame N to the
device. The first bit of TS26 of Frame (N-1) on the system side is con-
verted into the F-bit of Frame N to the device. TS0, TS16, TS27~TS31
and the other 7 bits in TS26 on the system side are all discarded.
2. T1/J1 Mode E1 Rate per One Filler Every Four CHs (refer to
Figure 25): The 8th bit of Frame N on the system side is converted to the
F-bit of the Frame N to the device. Then one byte of the system side is
discarded after the previous three bytes are converted into the device.
This process repeats 8 times and the conversion of one frame is com-
pleted. Then the process goes on.
3. T1/J1 Mode E1 Rate per Continuous CHs (refer to Figure 26):
TS1 to TS24 of Frame N on the system side are converted into Channel
1 to Channel 24 of Frame N to the device. The 8th bit of Frame N on the
system side is converted into the F-bit of Frame N to the device. The first
7 bits and TS25 to TS31 on the system side are all discarded.
Figure 24. E1 To T1/J1 Format Mapping - G.802 Mode
Figure 25. E1 To T1/J1 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
discarded
discarded
discardeddiscardeddiscarded
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
discarded
discarded
discarded
discarded
discarded