MPC8280 datasheet(1182/1386 Pages) FREESCALE

1182 / 1386 page

Inverse Multiplexing for ATM (IMA)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

34-36

Freescale Semiconductor

to the group order table not in use, and then IGRCNTL[GOTP] should be toggled. When the current

round-robin cell extraction process completes, the next process will use the new table.

This table alone defines the order of cell extraction from the delay compensation buffers. It is the

responsibility of software to read the LIDs of the links in the group from the received ICP cells during

group startup, and to program the group order table such that its order corresponds to the order of

increasing LIDs within the group.

The format of a receive group order table entry is shown in Figure 34-20.

Table 34-14 describes the format of a receive group order table entry.

34.4.5

IMA Link Tables

The IMA link tables consist of multiple IMA group structures indexed by the PHY address of their

corresponding PHYs. The transmit and receive parameters are located in separate tables. The IMA group

transmit and receive table entries are each 32 bytes long.

Note that to conserve memory space consumed by these tables, it is best to group the addresses of the

PHYs that are assigned as IMA. [For example, if out of eight total links only four are IMA, then optimally

these would be links 0 through 3.]

34.4.5.1

IMA Link Transmit Table Entry

Field

—

PHY ADDRESS

Figure 34-20. Receive Group Order Table Entry

Table 34-14. Receive Group Order Table Entry Field Descriptions

Bits

Name

Description

0–2

—

Reserved, initialize to zero.

3–7

PHY

ADDRESS

PHY address (up to 31 PHYs[0–30]) of the link transmitting in this position in the round-robin.

A value of 0x1F in this field indicates the end of the group order table.

Table 34-15. IMA Link Transmit Table Entry 1

Offset

Name

Width

Description

0x00

ILTCNTL

Byte

IMA link transmit control parameters.

0x01

ILTSTATE

Byte

IMA link transmit state. Microcode-managed parameter. Initialize to

zero at link startup.

0x02

LICPOS

Byte

Link ICP offset. Determines the position of the ICP cell within the IMA

frame. Program in the range 0 to M-1. See the IMA specification for

recommended methods for programming this field.

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