7
COMMERCIAL TEMPERATURE RANGE
IDT72V70200 3.3V TIME SLOT INTERCHANGE
DIGITAL SWITCH 512 x 5
12
CONNECTION MEMORY CONTROL
The CCO pin is a 4.096 Mb/s output, which carries 512 bits. The contents
of the CCO bit of each connection memory location are output on the CCO pin
once every frame. The contents of the CCO bits of the connection memory are
transmitted sequentially on to the CCO pin and are synchronous with the data
rates on the other serial streams.
The CCO bit is output one channel before the corresponding channel on
the serial streams. For example, the contents of the CCO bit in position 0 (TX0,
CH0) of the connection memory is output on the first clock cycle of channel 31
through CCO pin. The contents of the CCO bit in position 32 (TX1, CH0) of the
connection memory is output on the second clock cycle of channel 31 via CCO
pin.
If the ODE pin or the OSB bit is high, the OE bit of each connection memory
location controls the output drivers-enables (if high) or disables (if low). See
Table 4 for detail.
The processor channel (PC) bit of the connection memory selects between
Processor Mode and Connection Mode. If high, the contents of the connection
memory are output on the TX streams. If low, the stream address bit (SAB) and
the channel address bit (CAB) of the connection memory defines the source
information (stream and channel) of the time-slot that will be switched to the output
from data memory.
The V/C (Variable/Constant Delay) bit in each connection memory location
allows the per-channel selection between variable and constant throughput
delay modes.
If the LPBK bit is high, the associated TX output channel data is internally
looped back to the RX input channel (i.e., RX n channel m data comes from the
TX n channel m). If the LPBK bit is low, the loopback feature is disabled. For
proper per-channel loopback operation, the contents of the frame delay offset
registers must be set to zero.
INITIALIZATION OF THE IDT72V70200
After power up, the state of the connection memory is unknown. As such,
the outputs should be put in high impedance by holding the ODE low. While the
ODE is low, the microprocessor can initialize the device, program the active
paths, and disable unused outputs by programming the OE bit in connection
memory. Once the device is configured, the ODE pin (or OSB bit depending
on initialization) can be switched.
