Advance Information
MT90812
Each of the 32 channels of the 8 streams connecting the DX and IDX devices can be switched to any outgoing
channel and stream. This provides switching across all eight of the MT90812 devices.
3.2
IDX Link Mode
In IDX Link mode the expansion bus allows up to four IDX devices to be connected together as shown in Fig. 6.
The data flow between each MT90812 is supported on EST0 and EST1, two serial streams which operate at
8.192Mbit/s and each consist of 128 8-bit channels. The four MT90812 devices are labelled A, B, C and D.
TDM Link Mode can be used to link more than four MT90812 devices, refer to Section 3.1.
The expansion bus channel assignment for EST0 and EST1 in IDX Link mode is shown in Fig. 7. For the EST0
stream, each of the four MT90812 devices place data into 32 timeslots and read in data from the other 96
timeslots. The EBUS position, as defined in section “Control Register (CTL)” on page 54, designates which
timeslots the MT90812 writes to and which timeslots it reads from. For example, IDX A would output Channel 1
at the timeslot shown as A1 in Fig. 7 and input data during timeslots B1, C1 and D1.
For the EST1 stream, each MT90812 reads in 32 channels and can output data to the other 96 channels.
Which channels are read are also determined from the EBUS position bits. For example, IDX A will read data
during timeslots EA1, EA2,... EA32.
Each MT90812 will receive a total of 128 channels from the two streams EST0 and EST1. For IDX A, the 96
channels, B1-B32, C1-C32, D1-D32 will be taken from EST0 and 32 channels EA1-EA32 will be taken from
EST1.
A description of programming the switch in IDX Link mode is given in “Connection Memory” on page 10. The
Data Memory allocation is described in Section 5, “Address Memory Map”.
On power up, the EBUS is set to high impedance and the EBUS position bits must be programmed to avoid any
contention on the two streams.
Trunks
and Port
s
STi/o0
ST/o1
System Expansion bus (TDM)
IDX A
uport
Trunks
and Ports
STi/o0
STi/o1
IDX B
uport
Trunks
and Ports
STi/o0
STi/o1
IDX C
uport
MPU
Trunks
and Ports
STi/o0
STi/o1
IDX D
uport
Figure 6 - Four IDX Configuration using Expansion Bus IDX Link mode
frame n
F0i
EST0
EST1
A1
B1
C1
D1
A2
B2
C2
D2
A32 B32
C32
D32
EA1 EB1 EC1 ED1
EA32 EB32 EC32 ED32
Figure 7 - Expansion Bus - IDX Link mode
9
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