MT8986
bits as shown in table 8 (see IMS register). In case of
different I/O rates (DMO bit HIGH), the switching
configuration is always non-blocking with different
number of I/O streams which is defined by the IDR
and ODR bits (see IMS register).
register (SPS). The device clock for this operation is
4.096 MHz compatible to ST-BUS and GCI
interfaces. In addition, the per-channel selection
between variable or constant throughput delay is
available. This configuration is only provided in the
44 pin packages.
Identical Input/Output Data Rates
In case of nibble switching, 4-bit wide 32 kb/s data
channels can be switched within the device. In this
case, every serial stream is run at 2.048 Mb/s and
transports 64 nibbles per frame. When Nibble
Switching is selected at SCB bits, the MT8986
automatically assumes a 8 input x 4 output stream
configuration, providing a blocking switch matrix of
512 x 256 nibbles. If a non-blocking switch matrix is
required for nibble switching, the switch capacity is
reduced to 256 x 256 channel with a 4 input x 4
output configuration; the non-blocking matrix can be
arranged by the user by selecting any four of the 8
input streams. In nibble switching the interface clock
is 4.096 MHz.
When identical input/output data rate is selected by
the DMO bit, the I/O rate is determined by the IDR0-
1 bits, and the ODR0-1 bits are ignored. For each
data rate specified by the IDR bits, different
switching configurations can be selected in the
SCB1-0 bits.
Serial Links with Data Rates at 2.048 Mb/s
When 2.048 Mb/s data rate is selected at the IDR
bits, four different I/O configurations can be selected
by the SCB1-0 bits (see Table 8); 8 x 8, 16 x 8, 4 x 4
with stream pair selection and nibble switching.
Serial Links with Data Rates at 4.096 Mb/s
If 8 x 8 switching configuration is selected, a 256 x
256 channel non-blocking switching matrix is
available. In this configuration, the MT8986 device is
configured with 8 input and 8 output data streams
with 32 64 Kbit/s channels each. The interface clock
for this operation is 4.096 MHz with both ST-BUS
and GCI compatibilities and the per-channel
selection between variable and constant throughput
delay functions is provided. This configuration is
available in both the 40 and 44 pin packages.
Two I/O configurations can be enabled by the SCB
bits when input and output data rates are 4.096 Mb/s
on each serial stream: 8 x 4 and 4 x 4. When 8 x 4
switching configuration is selected, a 512 x 256
channel blocking switch is available with serial
streams carrying 64, 64 Kb/s channels each. For this
operation, a 4.096 MHz interface clock equal to the
bit rate should be provided to MT8986. Only variable
throughput delay mode is provided.
In 16 x 8 switching configuration, a 512 x 256
channel blocking switch matrix is available. This
configuration is only provided in the 44 pin package
and when the CPU interface is configured in
multiplexed bus mode. The device clock in this
application is 4.096 MHz, ST-BUS or GCI
compatible. This configuration only provides variable
throughput delay.
In case of 4 x 4 switching configuration, a 256 x 256
channel non-blocking switch is available with serial
streams carrying 64, 64 Kb/s channels each. In this
configuration, the interface clock is 4.096 MHz and
the per-channel selection between variable and
constant throughput delay operation is provided.
Figure 20 shows the timing for 4.096 Mb/s operation.
Serial Links with Data Rates at 8.192 Mb/s
If the stream pair selection switching configuration is
selected, only four input and four outputs (4 pairs of
serial streams) can be selected by the CPU to be
internally connected to the switch matrix, totalling a
128 x 128 channel non-blocking switch. From the 10
serial link pairs available, two pairs are permanently
connected to the internal matrix (STi0/STo0 and
STi1/STo1). An internal stream pair selection
capability allows two additional pairs of serial links to
be selected from the remaining 8 pairs (from STi/
STo2 to STi9/STo9) and be connected to the internal
matrix along with the permanently connected STi0/
STo0 and STi1/STo1 streams. The two additional pair
of streams called stream pair A and stream pair B,
should be selected in the Stream Pair Selection
Only 2 input x 2 output stream configuration is
available for 8.192 Mb/s, allowing a 256 x 256
channel non-blocking switch matrix to be
implemented. To enable this operation, the IDR bits
should be programmed to select 8.192 Mb/s rates
and the SCB bits have no effect. At 8.192 Mb/s,
every input and output stream provides 128 time-
slots per frame. The interface clock for this operation
should be 8.192 MHz. Figure 20 shows the timing for
8.192 Mb/s operation.
Table
1
summarizes the MT8986 switching
configurations for identical I/O data rates.
2-69
MITEL [ MITEL NETWORKS CORPORATION ]
