Freescale Semiconductor MPC8250, Family Reference Manual

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PCI Bridge
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
9-76 Freescale Semiconductor
An external PCI master reads the outbound queue port register. This causes the PCI bridge’s I
2
O unit to
read the MFA from local memory pointed to by the OPTPR+QBAR. The unit then advances the OPTPR.
When the FIFO is empty (head and tail pointers are equal), the unit returns 0xFFFF_FFFF.
The local processor posts MFAs to the outbound post list FIFO that is pointed to by the outbound
post_FIFO head pointer register, described in
Figure 9-71 and Table 9-56 . The local processor is
responsible for updating this register.
Figure 9-71. Outbound Post_FIFO Head Pointer Register (OPHPR)
Posted MFAs are picked up by PCI hosts that are pointed to by the outbound post_FIFO tail pointer
register, described in
Figure 9-72 and Table 9-57 . The PCI read is performed at the outbound queue port.
Hardware automatically advances this register after every read.
31 20 19 16
Field QBA OPHP
Reset 0000_0000_0000_0000
R/W R R/W
Addr 0x104D2
15 2 1 0
Field OPHP —
Reset 0000_0000_0000_0000
R/W R/W
R
Addr 0x104D0
Table 9-56. OPHPR Field Descriptions
Bits Name Description
31–20 QBA Queue base address. When read returns the contents of QBAR bits 31-20.
19–2 OPHP Outbound post_FIFO head pointer. Local memory offset of the head pointer of the outbound
post list FIFO.
1–0 — Reserved, should be cleared.