MPC8280 datasheet(381/1386 Pages) FREESCALE

381 / 1386 page

PCI Bridge

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

9-73

Figure 9-66. Inbound Free_FIFO Tail Pointer Register (IFTPR)

9.12.3.2.2

Inbound Post_FIFO Head Pointer Register (IPHPR) and

Inbound Post_FIFO Tail Pointer Register (IPTPR)

The inbound post FIFO holds MFAs from external PCI masters which are posted to the local processor.

PCI masters, external to the PCI bridge, write to the head of the FIFO by writing the MFA to IFQPR (refer

to Section 9.12.3.4.1, “Inbound FIFO Queue Port Register (IFQPR)”). The I2O unit transfers the MFA to

the location pointed to by the IPHPR. The local address is QBAR + IPHPR.

Once the MFA has been written to the queue in local memory, the PCI bridge’s I2O unit advances the

IPHPR to set up for the next message. This causes an interrupt to be asserted to the local processor. The

inbound post queue interrupt bit in the inbound interrupt status register (IMISR[IPQI]) is set to indicate

this condition (refer to Table 9-62). The local processor acknowledges the message (i.e. MFA) by writing

a one to the appropriate status bit (IMISR[IPQI]) to clear it. The local processor fetches the MFA by

reading the contents of the IPTPR. After the local processor has read the message pointed to by the MFA,

the local processor must advance the IPTPR. Once the processor has completed use of the message, it must

return the message buffer (i.e. MFA) to the inbound free list FIFO.

PCI masters post MFAs to the inbound post list FIFO that is pointed to by the inbound post_FIFO head

pointer register, described in Figure 9-67 and Table 9-52. The PCI writes are addressed to the inbound

queue port. Hardware (in the I2O module) automatically advances the IPHPR after every write.

Field

QBA

IFTP

Reset

0000_0000_0000_0000

R/W

Addr

0x104AA

Field

IFTP

—

Reset

0000_0000_0000_0000

R/W

Addr

0x104A8

Table 9-51. IFTPR Field Descriptions

Bits

Name

Description

31–20

QBA

Queue base address. When read returns the contents of QBAR bits 31-20.

19–2

IFTP

Inbound free_FIFO tail pointer. Local memory offset of the tail pointer of the inbound free list FIFO.

1–0

—

Reserved, should be cleared.

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