Attempted Reads From Rom On The Pci Bus—Host Mode - Motorola MPC8240 User Manual

Address Map Interactions
8.5.2.3 Attempted Reads from ROM on the PCI Bus—Host Mode
If the MPC8240 is in host mode, CDAR[CTT] indicates that the transferred address is for
local ROM space and the MPC8240 is configured for ROM on the PCI bus, then the
transaction is performed to the local ROM interface. Unknown data will be returned. (This
is considered a programming error.)
8.5.2.4 Attempted Reads from ROM on the Memory Bus
If the MPC8240 is in host mode, the CDAR[CTT] indicates that the transferred address is
for PCI ROM space and the MPC8240 is configured for ROM on the local memory
interface, then the transaction is issued to the PCI bus. The transaction will result in either
a master abort (and DSR[PE] is set) or an access to a configured device in the ROM address
space on the PCI bus.
8.5.3 Agent Mode Interactions
The following subsections describe interactions with the agent mode address maps.
8.5.3.1 Agent Mode DMA Transfers for PCI
When CDAR[CTT] indicates that the transferred address is for PCI, any address can be
issued within the 32-bit address space. If the software running on an MPC8240 configured
as an agent is aware of the system address map, it can perform DMA transfers with the
untranslated system address.
Alternatively, the MPC8240 agent DMA driver does not need to be aware of the system
memory map, and it can rely on address translation to be performed by the ATU. In this
case, transaction addresses should be programmed to fall within the outbound memory
window.
8.5.3.2 Accesses to Outbound Memory Window that Overlaps
0xFE00_00 – 0xFEEF_FFFF
For agent mode, if the outbound memory window is programmed to overlap the PCI's I/O
space (0xFE0x_xxxx – 0xFEBx_xxxx), PCI configuration space (0xFECx_xxxx –
0xFEDx_xxxx), or PCI interrupt acknowledge space (0xFEEx_xxxx), then a DMA
transaction to these address spaces results in a translated outbound address. Note that this
differs from a processor-generated transaction. In the case of a processor-generated
transaction to these spaces, these address ranges appear as holes in the outbound translation
window.
8.5.3.3 Attempted Accesses to Local ROM when ROM is on PCI
If the CDAR[CTT] indicates that the transferred address is for local ROM space and the
ROM is located on PCI, then the transaction is issued to local memory and results in
unknown data returned.
Chapter 8. DMA Controller 8-11