
XRT94L33
xr
Rev.1.2.0.
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
294
2.2.8.3.11.3
Forcing Negative-Stuff Pointer Adjustment Events via Software
The Transmit SONET POH Processor block permits the user to insert a “Positive-Stuff” pointer adjustment
event into the outbound STS-1 data-stream. This can be accomplished by inducing a “0 to 1 transition” within
Bit 3 (Insert Negative Stuff) within the “Transmit SONET Path – Transmit Path Control” register; as depicted
below.
Transmit SONET Path – Transmit Path Control Register (Address = 0xN9B7)
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.
A “negative-stuff” will occur (e.g., a single payload byte will be inserted into the “H3 byte” position, within the
outbound STS-1 data-stream).
The “D” bits, within the H1 and H2 bytes will be inverted (to denote a “Decrementing” pointer-adjustment
event).
The contents of the H1 and H2 bytes will be decremented by “1” and will be used as the new pointer from
this point on.
Note:
The contents of Bit 3 (Insert Negative 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.
2.2.8.3.11.4
Forcing a Single NDF Event via Software
The Transmit SONET POH Processor block permits the user to force a single NDF event into the outbound
STS-1 data-stream. This can be accomplished by executing the following steps.
STEP 1- Write the new “desired” pointer value into Bits 1 and 0 (H1 Pointer Value) within the
“Transmit SONET Path – Transmit Arbitrary H1 Pointer Register; and Bits 7 through 0 (H2 Pointer
Value) within the “Transmit SONET Path – Transmit Arbitrary H2 Pointer Register.
The bit-format of these two registers (with the relevant bit-fields shaded) is presented below.
Transmit SONET Path – Transmit Arbitrary H1 Byte Pointer Register (Address = 0xN9BF)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
NDF Bits
SS Bits
H1 Pointer Value
R/W
0
Transmit SONET Path – Transmit Arbitrary H2 Byte Pointer Register (Address = 0xN9C3)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
H2 Pointer Value[7:0]
R/W
0