![](http://datasheet.mmic.net.cn/Exar-Corporation/XRT94L33IB-L_datasheet_100163/XRT94L33IB-L_253.png)
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XRT94L33
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
Rev.1.2.0.
253
The “SS” bits, within the H1 byte, will be set to the value written into Bits 2 and 3 (SS Bits) within the
“Transmit STS-3c Path – Transmit Arbitrary H1 Byte Pointer Register.
The 10-bit pointer value (within bits 7 and 8, within the H1 byte, and all eight bits within the H2) will be set to
the values written into Bits 1 and 0 (H1 Pointer) within the “Transmit STS-3c Path – Transmit Arbitrary H1
Byte Pointer” register, and Bits 7 through 0 (H2 Pointer Value) within the “Transmit STS-3c Path – Transmit
Arbitrary H2 Byte Pointer” Register.
2.2.7.3.11.1
Forcing Positive-Stuff Pointer Adjustment Events via Software
The Transmit STS-3c POH Processor block permits the user to insert a “positive-stuff” pointer adjustment
event into the outbound STS-3c data-stream. This can be accomplished by inducing a “0 to 1” transition in Bit
2 (Insert Positive Stuff) within the “Transmit STS-3c Path – Transmit Path Control” Register, as depicted
below.
Transmit STS-3c Path – Transmit Path Control Register (Address = 0x19B7)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Pointer
Force
Check Stuff
Insert
Negative
Stuff
Insert
Positive
Stuff
Insert
Continuous
NDF Events
Insert Single
NDF Event
R/O
R/W
W
R/W
0
0 -> 1
0
Once the user induces this “0 to 1 transition” in Bit 2, then the following events will occur.
A “positive-stuff” will occur (e.g., a single stuff byte will be inserted into the STS-3c data-stream,
immediately after the H3 byte position).
The “I” bits, within the H1 and H2 bytes will be inverted (to denote an “Incrementing” Pointer Adjustment)
event.
After the “positive-stuff” event, the pointer (consisting of the H1 and H2 bytes) will be incremented by “1”
and will be used as the new pointer from this point on.
Note:
The contents of Bit 2 (Insert Positive Stuff) will be automatically cleared after the user has written a “1” into this
bit-field. Hence, there is no need for the user to go back and write a “0” into this bit-field.
2.2.7.3.11.2
Forcing Negative-Stuff Pointer Adjustment Events via Software
The Transmit STS-3c POH Processor block permits the user to insert a “Positive-Stuff” pointer adjustment
event into the outbound STS-3c data-stream. This can be accomplished by inducing a “0 to 1 transition”
within Bit 3 (Insert Negative Stuff) within the “Transmit STS-3c Path – Transmit Path Control” register; as
depicted below.
Transmit STS-3c Path – Transmit Path Control Register (Address = 0x19B7)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Unused
Pointer
Force
Check Stuff
Insert
Negative
Stuff
Insert
Positive
Stuff
Insert
Continuous
NDF Events
Insert
Single NDF
Event
R/O
R/W
W
R/W
0
0 ->1
0
Once the user induces a “0 to 1” transition in Bit 3, then the following events will occur.