CMOS
mode requires a CLK of 8.192 MHz and allows a
maximum non-blocking capacity of 1,024 x 1,024
channels.
8.192 Mb/s Serial Links (DR0=0, DR1=1)
When the 8.192 Mb/s data rate is selected, the
device is configured with 16-input/16-output data
streams each having 128 64 kb/s channels. This
mode requires a CLK of 16.384 MHz and allows a
maximum non-blocking capacity of 2,048 x 2,048
channels. Table 1 summarizes the switching
configurations and the relationship between different
serial data rates and the master clock frequencies.
Serial
Interface
Data Rate
2 Mb/s
4 Mb/s
8 Mb/s
Master Clock
Required
(MHz)
4.096
8.192
16.384
Matrix
Channel
Capacity
512 x 512
1,024 x 1,024
2,048 x 2,048
MT90823
The SFE bit must be set to zero before starting a
new measurement cycle.
In ST-BUS mode, the falling edge of the frame
measurement signal (FE) is evaluated against the
falling edge of the ST-BUS frame pulse. In GCI
mode, the rising edge of FE is evaluated against the
rising edge of the GCI frame pulse. See Table 10 and
Figure 3 for the description of the frame alignment
register.
This feature is not available when the WFP Frame
Alignment mode is enabled (i.e., when the WFPS pin
is connected to VDD).
Memory Block Programming
The MT90823 provides users with the capability of
initializing the entire connection memory block in two
frames. Bits 11 to 15 of every connection memory
location will be programmed with the pattern stored
in bits 5 to 9 of the IMS register.
The block programming mode is enabled by setting
the memory block program (MBP) bit of the control
register high. When the block programming enable
(BPE) bit of the IMS register is set to high, the block
programming data will be loaded into the bits 11 to
15 of every connection memory location. The other
connection memory bits (bit 0 to bit 10) are loaded
with zeros. When the memory block programming is
complete, the device resets the BPE bit to zero.
Loopback Control
Table 1- Switching Configuration
Input Frame Offset Selection
Input frame offset selection allows the channel
alignment of individual input streams to be offset with
respect to the output stream channel alignment (i.e.
F0i). This feature is useful in compensating for
variable path delays caused by serial backplanes of
variable lengths, which may be implemented in large
centralized and distributed switching systems.
Each input stream can have its own delay offset
value by programming the frame input offset (FOR)
registers. Possible adjustment can range up to +4
master clock (CLK) periods forward with resolution of
1/2 clock period. The output frame offset cannot be
offset or adjusted. See Figure 4, Table 11 and Table
12 for delay offset programming.
Serial Input Frame Alignment Evaluation
The MT90823 provides the frame evaluation (FE)
input to determine different data input delays with
respect to the frame pulse F0i.
A measurement cycle is started by setting the start
frame evaluation (SFE) bit low for at least one frame.
Then the evaluation starts when the SFE bit in the
IMS register is changed from low to high. Two frames
later, the complete frame evaluation (CFE) bit of the
frame alignment register (FAR) changes from low to
high. This signals that a valid offset measurement is
ready to be read from bits 0 to 11 of the FAR register.
The loopback control (LPBK) bit of each connection
memory location allows the ST-BUS output data to
be looped backed internally to the ST-BUS input for
diagnostic purposes.
If the LPBK bit is high, the associated ST-BUS output
channel data is internally looped back to the ST-BUS
input channel (i.e., data from STo
n
channel
m
routes
to the STi
n
channel
m
internally); if the LPBK bit is
low, the loopback feature is disabled. For proper
per-channel loopback operation, the contents of
frame delay offset registers must be set to zero.
Delay Through the MT90823
The switching of information from the input serial
streams to the output serial streams results in a
throughput delay. The device can be programmed to
perform time-slot interchange functions with different
throughput delay capabilities on a per-channel basis.
For voice application, select variable throughput
9
MITEL [ MITEL NETWORKS CORPORATION ]
