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XRT94L43
25
SONET/SDH OC-12 TO 12XDS3/E3 MAPPER
REV. 1.0.2
G4
TxTOHFrame
O
CMOS
Transmit TOH Input Port - STS-12/STM-4 Frame Indicator:
This output pin, along with TxTOHClk, TxTOHEnable output pins, and
the TxTOH and TxTOHIns input pins function as the Transmit TOH Input
Port.
This output pin will pulse "High" (for one period of TxTOHClk), one
TxTOHClk clock period prior to the first TOH bit of a given STS-12
frame, being expected via the TxTOH input pin.
If it is desired to externally insert a value of TOH into the outbound STS-
12 data stream via the Transmit TOH Input Port, then do the following:
Continuously sample the state of TxTOHEnable and this output pin
upon the rising edge of TxTOHClk.
Whenever the TxTOHEnable output pin pulse "High", then the user's
external circuitry should drive the TxTOHIns input pin "High".
Next, the user should output the next TOH bit, onto the TxTOH input
pin, upon the falling edge of TxTOHClk.
NOTE: The external circuitry (which is being interfaced to the Transmit
TOH Input Port can use this output pin to denote the boundary
of STS-12 frames.
C1
TxTOHIns
I
TTL
Transmit TOH Input Port - Insert Enable Input Pin:
This input pin, along with the TxTOH input pin, and the TxTOHEnable,
TxTOHFrame and TxTOHClk output pins function as the Transmit TOH
Input Port.
This input pin is used to either enable or disable the Transmit TOH Input
Port.
If this input pin is "Low", then the Transmit TOH Input Port will be dis-
abled and will not sample and insert (into the outbound STS-12 data
stream) any data residing on the TxTOH input, upon the rising edge of
TxTOHClk.
If this input pin is "High", then the Transmit TOH Input Port will be
enabled. In this mode, whenever the TxTOHEnable output pin is also
"High", the Transmit TOH Input Port will sample and latch any data that
is presented on the TxTOH input pin, upon the rising edge of TxTOHClk.
If it is desired to externally insert a value of TOH into the outbound STS-
12 data stream via the Transmit TOH Input Port, then do the following:
Continuously sample the state of TxTOHFrame and TxTOHEnable
upon the rising edge of TxTOHClk.
Whenever the TxTOHEnable output pin is sampled "High" then the
user's external circuitry should drive this input pin "High".
Next, the user should output the next TOH bit, onto the TxTOH input
pin, upon the falling edge of TxTOHClk. The Transmit TOH Input Port
will sample the data (on this input pin) upon the rising edge of
TxTOHClk.
NOTE: Data applied to the TxTOH input pin will be ignored (e.g., not
sampled) unless then the TxTOHEnable and this input pin are
each "High".
SONET/SDH OVERHEAD INTERFACE - TRANSMIT DIRECTION
PIN #SIGNAL NAME
I/O
SIGNAL
TYPE
DESCRIPTION