Freescale Semiconductor MPC8260 - Manual (Page 1142)

Inverse Multiplexing for ATM (IMA)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
33-40 Freescale Semiconductor
Table 33-13 describes the IRGFS bit fields.
33.4.4.2.4 Receive Group Order Tables
The receive group order tables define the order of the links in the round-robin extraction of cells to the
links of the IMA group. The table consists of an array of bytes ordered from first link to last link, with each
byte providing the PHY address of its associated link. The end of the table is indicated by an entry
programmed to 0x1F.
Two group order tables are used in order to allow for on-the-fly changes (i.e. to add or remove links), while
making certain that the changes only occur at the end of a round-robin cycle. IGRCNTL[GOTP] indicates
which group order table pointer (and therefore, group table) is currently in use. Changes should be made
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 33-20 .
Table 33-14 describes the format of a receive group order table entry.
0 1 6 7
Field 0 — GSC-M
Figure 33-19. IMA Receive Group Frame Size (IGRSTATE)
Table 33-13. IRGFS Field Descriptions
Bits Name Description
0 0 Reserved, initialize to zero.
1-5 — Reserved, initialize to zero.
6-7 GSC-M IMA Receive Group Frame Size
Bits 0-5: Reserved
Bits 6-7 - GSC_M: Value of received ICP cell Group Status Contl field
(Bits 1:0) which determine the IMA frame size. This field must be
programmed before links in the group are assigned
0 2 3 7
Field — PHY ADDRESS
Figure 33-20. Receive Group Order Table Entry