Freescale Semiconductor MPC8260 - Manual (Page 1143)

Inverse Multiplexing for ATM (IMA)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 33-41
33.4.5 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.]
33.4.5.1 IMA Link Transmit Table Entry
Table 33-14. 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 33-15. 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.
0x03 ILID Byte IMA link ID. Formatted per the Cell ID and Link ID field of an ICP cell.
Bit 0: 1 (indicating ICP cell)
Bits 1-2: Not Used, set to zero
Bits 3-7: Program to software-assigned LID.
[Note: This value is only used by microcode to format ICP cells for this
link, it is not used to determine round-robin transmission order. That
function is performed by the group order table.]
0x04 ITSEC Word IMA transmit stuff event counter. While ILTCNTL[SES]=0, increments
each time a stuff event is performed on this link. Initialize to zero at link
startup.
0x08 ITQSP Hword IMA link transmit queue start pointer. This parameter forms bits 12-27
of the pointer; bits 0-11 are from IMAEXTBASE, and bits 28-31 are
zero. Refer to
Section 33.4.6.1, “Transmit Queues.”
0x0A ITQEP Hword IMA link transmit queue end pointer. This parameter forms bits 12-27
of the pointer; bits 0-11 are from IMAEXTBASE, and bits 28-31 are
zero. Points to the last cell in the transmit queue. Program this
parameter to ITQSP+TQ_SIZE-4. Refer to
Section 33.4.6.1, “Transmit
Queues.”