xrt94l33 Exar Corporation, xrt94l33 Datasheet - Page 37

• Manufacturer Part Number: xrt94l33
• Description: Multi-channel, Multi-function Device Aggregates 3 Ds3/e3/sts-1 Into Oc3/stm-1
• Manufacturer: Exar Corporation

xr
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
AB16
E12
E17
TxOH_0
TxOH_1
TxOH_2
I
TTL
Continued
If the user is inserting both POH and TOH data via these
input pins:
In this mode, the external circuitry (which is being interfaced to
the “Transmit Path Overhead Input Port” is suppose to monitor
the following output pins.
• TxOHFrame_n
• TxOHEnable_n
• TxOHClk_n
The “TxOHFrame_n” output pin will toggle “high” twice during
a given STS-1 frame period. First, this output pin will toggle
high coincident with the “TxOH” port being ready to accept and
process the A1 byte (e.g., the very first TOH byte). Second,
this output pin will toggle “high” coincident with the “TxOH” port
being ready to accept and process the J1 byte (e.g., the very
first POH byte).
If the externally circuitry samples the “TxOHFrame_n” output
pin “high”, and the “TxOHEnable_n” output pin “low”, then the
“TxOH” port is now ready to accept and process the very first
TOH byte.
If the externally circuitry samples the “TxOHFrame_n” output
pin “high” and the “TxOHEnable_n” output pin “high”, then the
“TxOH” port is now ready to accept and process the very first
POH byte.
To externally insert a given POH or TOH byte;
This data bit will be sampled upon the very next falling edge of
“TxOHClk_n”. The external circuitry should continue to keep
the “TxOHIns_n” input pin “high” and advancing the next bits
(within the POH bytes) upon each rising edge of “TxOHClk_n”.
37
(1) assert the “TxOHIns_n” input pin by toggling it “high”,
(2) place the value of the first bit (within this particular
and
POH or TOH byte) on this input upon the very next
falling edge of “TxOHClk_n”
XRT94L33
Rev.1.2.0.