ZL30226/GA ZARLINK [Zarlink Semiconductor Inc], ZL30226/GA Datasheet - Page 51

• Manufacturer Part Number: ZL30226/GA
• Description: 4/8/16 Port IMA/TC PHY Device for xDSL
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

3.3.13.5
The values and delay type for a selected link(s) or IMA Group can be read using the RX Delay Select (0x02AA)
register.
IMA Group delay types include: the Maximum Delay over time; the Current Maximum Delay and the Current
Minimum Delay of an IMA Group. Current Link Delay reports the Current Delay of a link. These values are all
reported through a common RX Delay (0x0285) register. The value is in number of cells. All delay values include
the guardband delay value. The RX Delay Link Number (0x0286) register reports the link number associated with
the delay value that is currently in the RX Delay (0x0285) register, with the exception for the Maximum Delay over
time value, where the link number reported is not valid (reports value of 0).
The Maximum Delay over time value can be reset at any time by writing a clear command to bit 6 in the RX
Delay Select (0x02AA) register. Note the value of the Maximum Delay over time is updated once per IMA
frame, hence it an take up to one IMA frame for the value to be updated after it is reset. A value of 0xFE00
(negative 0) is read immediately after a reset command.
The differential delays can be easily obtained by subtracting the delay values of the links.
3.3.13.6
If a link to be added has a delay value which falls beyond the worst current delay value, then there are 2 options:
either reject the link or re-adjust the pointers. To re-adjust the pointers, the number of cells to be added (delta) is
specified and corresponds to the amount of extra delay to be added to the current recombination delay. The
additional delay is first programmed in the Guardband/Delta Delay (0x0287-0x028E) registers and then a
command to increase the delay is issued (using the Increment Delay Control (0x0281) and Decrement Delay
Control (0x0282) registers). The ZL30226/7/8 device stops the recombiner process for the amount of time specified
and then resumes the recombiner process. No cells are lost but there is an effect on the CDV. The increment process
is completed when the control bit in the Increment Delay Control (0x0281) or Decrement Delay Control (0x0282)
register is returned to a 0 value.
If the link exhibiting the longest transmission delay is removed, the recombiner delay can be reduced accordingly.
When such a correction occurs, the number of cells corresponding to the delay correction will be lost. To reduce the
impact of this correction, its implementation can either be immediate or delayed. The Increment Delay Control
(0x0281) and Decrement Delay Control (0x0282) registers are used for this purpose. The amount of delay to be
removed (i.e., number of cells) in the recombiner process is controlled by the RX Guardband/Delta Delay
(0x0287-0x028E) register. Alternatively, the links can all be placed in blocking mode for the transition period to avoid
losing any cells.
If a decrement delay command is issued which would result in a negative delay value on one or more links, the
following action will take place: the read pointer is re-adjusted as required by the decrease delay command and since
the delay is negative, the recombiner process is suspended until the delay on all the links at least reach a positive
value of 4. Then, the recombiner process will resume.
3.3.14
A quick initialization sequence for the RX IMA Group could be as follows (default values can be used for some
registers).
(Note: The startup procedure below is to indicate the most important steps. A more detailed and complete
sequence can be found in the Zarlink IMA Core software).For ZL30226 only groups 0, 1, 2 and 3 are used.
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Configure the SRAM parameters using the SRAM Control (0x0299), RX External SRAM Control (0x0284)
and Global Debug bit in the ICP Cell RAM DEBUG (0x0108) registers
Configure the Cell delineation and IMA Frame State Machines parameters by writing to the Cell Delineation
(0x00C9), Loss of Delineation (0x00C8) and IMA Frame Delineation (0x00CA) registers
RX IMA Group Start-Up
Measured Delay Between Links
Incrementing/Decrementing the Recombiner Delay
Zarlink Semiconductor Inc.
ZL30226/7/8
51
Data Sheet