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MPC8240 Integrated Processor User’s Manual
I
2
O Interface
9.3.3 FIFO Descriptions
There are two paths for messages—an inbound queue to receive messages from the remote
host (and other IOPs) and an outbound queue to pass messages to a remote host. Each queue
is implemented as a pair of FIFOs. The inbound and outbound message queues each
consists of a free_list FIFO and a post_list FIFO.
Messages are comprised of frames that are at least 64 bytes long. The message frame
address (MFA) points to the first byte of the message frame. The messages are located in a
pool of system memory (any memory address accessible through the PCI bus). Tracking of
the status and location of these messages is done with the four FIFOs that are located in
local memory. One FIFO in each queue tracks the free MFAs (free_list FIFO). The other
FIFO tracks the MFAs that have posted messages (post_list FIFO). These FIFOs are
managed by the remote processors and the processor core through the MPC8240 I
2
O
registers. For more information, see Section 9.3.2, “I2O Register Summary”.
—
0x0_0120
IFHPR
Inbound free_FIFO head pointer register
—
0x0_0128
IFTPR
Inbound free_FIFO tail pointer register
—
0x0_0130
IPHPR
Inbound post_FIFO head pointer register
—
0x0_0138
IPTPR
Inbound post_FIFO tail pointer register
—
0x0_0140
OFHPR
Outbound free_FIFO head pointer register
—
0x0_0148
OFTPR
Outbound free_FIFO tail pointer register
—
0x0_0150
OPHPR
Outbound post_FIFO head pointer register
—
0x0_0158
OPTPR
Outbound post_FIFO tail pointer register
—
0x0_0164
MUCR
Messaging unit control register
—
0x0_0170
QBAR
Queue base address register. Must be set on 1-Mbyte boundary
Table 9-7. I
2
O Register Summary (Continued)
PCI Offset
Local Memory
Offset
Acronym
Name
Содержание MPC8240
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