Freescale Semiconductor MPC8260 - Manual (Page 1150)

Inverse Multiplexing for ATM (IMA)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
33-48 Freescale Semiconductor
33.4.5.3 IMA Link Receive Statistics Table
The IMA link receive statistics table is optional. It is enabled globally for this FCC via IMACNTL[IRSE].
The base of this table is determined by IRLINKSTAT. Entries in the table are indexed by the link number
of the associated link. The format for the IMA link receive statistic table entries is shown in
Table 33-22
33.4.6 Structures in External Memory
The IMA microcode requires supporting queue structures in external memory. These are used for the jitter
buffers (on transmission) and the delay compensation buffers (on reception). These structures reside in a
1 megabyte memory region defined by IMAEXTBASE, and may reside on either the 60x bus or the local
bus, as defined by IMACNTL[DSB].
33.4.6.1 Transmit Queues
Transmit queues are allocated on a per-link basis. They are circular queues of 64-byte buffers, defined by
their start and end pointers. For the transmit queue of the timing reference link (TRL), the queue must
consist of a minimum of four buffers (although it may consist of five buffers, if consistency of data
structures is desired). For the transmit queues of non-TRL links, the queues must consist of five buffers.
Queue fill and extract pointers must be initialized by software to the start of the queue; thereafter, these
pointers are managed by the microcode. The queue pointers must be on a 64-byte aligned boundary.
Figure 33-26. IMA Transmit Queue
Table 33-22. IMA Link Receive Statistics Table Entry
Offset Name Width Description
0x00 ICPVIOL Word IMA receive ICP violation event counter. While ILRCNTL[SES]=0,
increments each time an errored, invalid, or missing ICP cell is received
on this link. Initialize to zero at link startup.
0x04 OIF Word Out-of-IMA frame counter. While ILRCNTL[SES]=0, increments each
time an Out-of-IMA Frame anomaly occurs on this link. Initialize to zero
at link startup.
IMA External Structure Region
Transmit
IMAEXTBASE Queue ITQSP
bits 0-11 bits 12-27
0000
bits 28-31
IMAEXTBASE ITQEP 0000
IMAEXTBASE
64-byte boundary
ITQSP + TQ_SIZE - 4