QT2022/32 - Data Sheet: DS3051
ified number of frames. The control bit initiates byte insertion for all 3 bytes simultaneously. It will only trigger byte
insertion if a fixed number of frames is selected. To initiate insertion multiple times, toggle the control bit.
The byte values to be inserted are stored in 3 separate registers, in the lower 8 bits of MDIO registers 2.C604h -
2.C606h.
Figure 15: TX WIS Overhead Insertion Control Register
TX WIS Overhead Insertion Control Registers
15 14 13 12 11 10 9
15 14 13 12 11 10 9
8
8
8
7
7
7
6
6
6
5
5
5
4
4
4
3
3
3
2
2
2
1
1
1
0
0
0
Byte1 (2.C601h)
Byte2 (2.C602h)
Byte3 (2.C603h) 15 14 13 12 11 10 9
Frame
Count
STS-1 Frame Number
(0 to 191)
Row
Number
(0 to 8)
Column
Number
(0 to 3)
Frame Count Decoding
00 : One (1) frame
01 : Five (5) frames
10 : Seven (7) frames
11 : Continuous (all frames)
To initiate insertion, first set the programmable registers then set the Control enable signals. The insertion will hap-
pen on the next frame. The priority of the insertion goes from Register 1 to 3.
If the registers are set for B1, B2, B3 locations the byte will be treated as a mask to corrupt specific bits in the Parity
bytes.
Byte Insert Priority
The overhead byte insertion is prioritized, with Byte1 receiving the highest priority and Byte3 the lowest. This
means that, in the event of a conflict in the byte insert settings the instructions for Byte1 will be executed preferen-
tially, followed by Byte2 and then Byte3. A conflict arises when two different Bytes are programmed to overwrite the
same overhead byte field.
This behavior can be used for testing purposes to generate more complex OH byte insert sequences. For example,
Byte1, Byte2 and Byte3 can be programmed to insert different values to the same overhead byte. By selecting a
finite Frame Count for Byte1 and Byte2, the WIS block will first execute the instructions for Byte1 for the pro-
grammed number of frames, followed immediately by Byte2 on the next frame and finally Byte3. In this example,
Byte3 may be programmed to insert for either a finite or continuous Frame Count. If a continuous Frame Count is
selected for Byte1 or Byte2, the WIS block will never execute the instructions for the subsequent Bytes.
50
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