VSC7440 datasheet(262/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

245

Configure other DTI parameters. For more information, see Table 163, page 235.

3.25.7

Starting Injection

TTI is enabled by using TTI_INIT to initialize and then setting TTI_ENA = 1.

Each TTI is started by setting TIMER_LEN a non-zero value.

Each DTI is started by setting DTI_CTRL.ENA = 1.

3.25.8

Stopping Injection

Each TTI is stopped by setting TIMER_LEN to 0.

All TTIs can be stopped by setting TTI_ENA = 0.

Each DTI is stopped by setting DTI_CTRL.ENA = 0.

3.25.9

Removing Injection Frames

This section provides information about removing a single frame (TTI) or frame sequence (DTI) from the

buffer memory.

3.25.9.1 Single Frame (TTI)

To remove a single frame from buffer memory, the frame must be injected one more time. This “removal

injection” does not result in a frame transmission, but purely serves to remove the frame from the buffer

memory.

Use the following procedure to remove a single frame from buffer memory.

Set the FRM_RM bit for frame in the frame table.

For TTI: Set TIMER_LEN to 0x1ff.

Poll the FRM_GONE bit until it gets set by AFI.

When performing removal injection, injection must be enabled for the corresponding port by setting

AFI:PORT_TBL[<port>]:PORT_CFG.FRM_OUT_MAX != 0.

3.25.9.2 Frame Sequence (DTI)

Use the following procedure to remove a DTI frame sequence from buffer memory.

Disable the DTI by setting DTI_CTRL.ENA = 0.

Set the FRM_RM bit for each frame to be removed in the frame table.

Set DTI_FRM.NEXT_FRM_PTR to DTI_FRM.FIRST_FRM_PTR.

Set DTI_MODE.MODE = 0.

Set DTI_CNT.CNT = 1.

Set DTI_MODE.FRM_INJ_CNT to 0.

Optionally, set all delays in sequence to 0 to speed up the removal procedure.

Set DTI_CNT_DOWN.CNT_DOWN to 0.

Enable the DTI by setting DTI_CTRL.ENA = 1.

10. Poll the FRM_GONE for the last frame to be removed until the bit gets set by AFI.

This procedure causes the frames to be injected one last time and through this, be removed from buffer

memory. The frames will not actually be transmitted on the destination port.

When performing removal injection, injection must be enabled for the corresponding port by setting

AFI:PORT_TBL[<port>]:PORT_CFG.FRM_OUT_MAX != 0.

3.25.10 Port Parameters

To ensure that the queue system does not overflow with injected frames, for example, if a port is in flow

control, an upper bound on the number of injected, but not yet transmitted, frames per port can be

configured in FRM_OUT_MAX.

If FRM_OUT_MAX is reached, then any DTI injections are postponed until the number of outstanding

frames falls below FRM_OUT_MAX. TTI injections uses a slightly higher limit of

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