MPC8280 datasheet(331/1386 Pages) FREESCALE

331 / 1386 page

PCI Bridge

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

9-23

NOTE

When a transaction is performed by a PCI master, the bridge checks the

address against inbound ATUs and if it does not hit, it then checks against

PIMMR; if it is a hit, the bridge translates it to a 60x cycle. Because PIMMR

does not have an associated translation register and window size definition,

the translation is performed as follows: a 128-Kbyte window is provided for

the PCI master to access the MPC8280’s internal (dual port) registers. It

translates to the MPC8280’s IMMR value for the upper bits of the address.

This allows the PCI master to access any of the PCI-bridge registers without

wasting an inbound translation window. In effect, there are a total of three

inbound windows, 2 with ATUs and 1 with PIMMR.

Transactions initiated by the DMA controller or message unit fall into one of the following cases:

•

If the transaction address is within one of the outbound PCI translation windows, the transaction is

sent to the PCI bus with address translation.

•

If the transaction address is not within a PCI translation window, the transaction is sent to the core

side of the PCI bridge with no address translation.

An address decode flow chart for transactions from the DMA controller or message unit to the PCI bridge

is shown in Figure 9-13.

Figure 9-13. Address Decode Flow Chart for Embedded Utilities

(DMA, Message Unit) Mastered Transactions

Example address mappings of these different types of transactions are shown in Figure 9-14. Note that the

translation mechanism shown is an example only; the address translation, as well as the memory and I/O

destinations, can be programmed independently for each address translation window.

Yes

DMA/MU mastered

transaction

Issue transaction

with translated

address to PCI

Issue transaction

with un-translated

address to 60x bus

Hit

Outbound ATU

MPC8280 Datasheet(PDF) 331 Page - Freescale Semiconductor, Inc