AN1849 Motorola / Freescale Semiconductor, AN1849 Datasheet - Page 17

• Manufacturer Part Number: AN1849
• Description: MPC107 Design Guide
• Manufacturer: Motorola / Freescale Semiconductor

in any order, ROMs have particular (predefined) associations associated with the data bits. This is not only
true with externally programmed ROMs, but programmable flash memories assign particular meanings to
the data bits, so it is generally recommended to connect the MSB of the Flash/ROM (D7 or D15, depending
on size) to the corresponding MSB of the PowerPC data bus byte lane (MDH0/MDL0, MDH8/MDL8,
MDH16/MDL16, and MDH24/MDL24, again depending on the device size).
1.6 PCI Interface
The PCI interface of the MPC107 has several enhancements over the MPC106, in particular full support for
66 MHz PCI operation and the ability to configure the part as an agent (with support for programmable
inbound and outbound address ranges set by an external PCI master). There are several differences between
host mode and agent mode, which are summarized in Table 9.
The agent mode feature is possible due to the addition of the ITU (Inbound Translation Unit); when the
MPC107 is set to Agent mode, it will accept configuration cycles when the IDSEL pin is asserted. This new
feature allows multiple MPC107s to co-exist on the same PCI bus, which is extremely difficult for
MPC106-based systems to accomplish. An example multiple-MPC107 system is shown in Figure 11.
IDSEL
MPC107 Registers
accessible from
PCI
Multiple MPC107s
supported
INTA
Feature
must be grounded
Host Mode
Partially
Yes
Table 9. MPC107 Host and Agent Differences
No
MPC107 Design Guide
must be connected
to an AD(31:0) pin
Agent Mode
Yes
Yes
Yes
The MPC107 only allows configuration cycles
when in agent mode.
Only embedded functions can be accessed on
a host (I
processor configuration registers are
inaccessible (MCCR1, PICR1, etc.).
Only one MPC107 may serve as the host (this
is true of PCI hosts in general).
In host mode, INTA cannot be wired to
INT(0:4)
2
O, DMA, etc.). Standard memory and
Description
PCI Interface
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