MT90812 Mitel Networks Corporation, MT90812 Datasheet - Page 26

• Manufacturer Part Number: MT90812
• Description: Integrated Digital Switch (IDX)
• Manufacturer: Mitel Networks Corporation

MT90812
(OE) bit of Local (or Expansion depending on the output stream number) Connect Memory High must be set to
0 in order to put the output driver of the corresponding stream into high-impedance state during the selected
timeslot.
7.0
Gain Control is provided on the outgoing channels, with a range of +3 to -27 dB in steps of 1dB, as well as -
dB in steps of 3 dB. Refer to Section 6.0 for a description of gain control for a conference.
Outgoing gain control of +3 to -27 dB in steps of 1dB, as well as - dB is also provided on the 32 tones from the
Tone generator.
The gain for each outgoing channel is specified in Connect Memory High. Refer to “Connection Memory High”
on page 50. There are five bits G4-G0 which are used to set the gain. If 0 dB value is selected then the gain
control circuitry is bypassed. Otherwise the 8 bit PCM value for the outgoing channel is read from Data
Memory, expanded to a 14 bit linear PCM value, multiplied by the appropriate gain factor, and compressed to
an 8 bit PCM value, before being output on the outgoing serial stream.
The output of the tone generator and conference blocks are multiplied by the gain factor specified for the tone
or conference party and stored as a 14 bit linear PCM value in Data Memory. When the outgoing channel is
connected to a tone or conference output location, the 14 bit linear PCM value is then read from DM, multiplied
by the gain factor specified for the outgoing channel, and compressed to an 8 bit PCM value, before being
output on the outgoing serial stream.
8.0
A delay results when transferring channel information from a MT90812 local input stream to an output stream.
This delay varies according to the switch mode programmed in the CST bit of connect memory high; i.e.
Minimum or Constant Throughput Delay Mode.
8.1
In Minimum Delay Mode the delay is dependent on the combination of source and destination channels, the
input and output streams and the data rate of the expansion bus.
Data transfers between streams operating at the same data rate (i.e. Sti1 to Sto1, Est1 to Est0, etc.) can be
described as follows. Channel information for a particular timeslot n from the input stream is sent to Data
Memory in timeslot n+1. Channel information is queued for an output channel n in timeslot n-1. Thus,
information entering the MT90812 from timeslot n, cannot be transmitted in the same timeslot n or timeslot
n+1, without a frame delay. Information switched to a timeslot of m=n+2 or later will be switched within the
same frame. The relationship that is required between incoming and outgoing timeslots are shown in Table 6.
For all but four cases, if the outgoing timeslot, m, is greater than or equal to n+2, the data is switched within the
same frame. The throughput delay is m-n timeslots.
There are four cases where there are data transfers between streams operating at different data rates. This
occurs when the expansion bus is running at 4.096Mb/s or 8.192 Mb/s and the data is transferred between the
expansion bus and either Sto0 or Sto1. The channel numbers range from 0 to 31 for a stream operating at
2.048Mb/s, and from 0 to 63 and 0 to 127 for streams operating at 4.096Mb/s and 8.192 Mb/s, respectively.
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dB. If a channel is in a conference, incoming and/or outgoing gain control is provided, with a range of 0 to -9
Gain Control
Delays Through the MT90812
Minimum Delay Mode (CST bit=0)
Advance Information