Freescale Semiconductor MPC8260 8.2 Bus Configuration

The 60x Bus
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
8-2 Freescale Semiconductor
8.2 Bus Configuration
The 60x bus supports separate bus configurations for internal masters and external bus masters.
• Single-PowerQUICC II bus mode connects external devices by using only the memory controller.
This is described in Section 8.2.1, “Single-PowerQUICCII Bus Mode.”
• The 60x-compatible bus mode, described in Section 8.2.2, “60x-Compatible Bus Mode,” enables
connections to other masters and 60x-bus slaves, such as an external L2 cache controller.
The figures in the following sections show how the PowerQUICCII can be connected in these two
configurations.
8.2.1 Single-PowerQUICC II Bus Mode
In single-PowerQUICC II bus mode, the PowerQUICC II is the only bus device in the system. The internal
memory controller controls all devices on the external pins. Figure8-1 shows the signal connections for
single-PowerQUICC II bus mode.
Parking Granting potential bus mastership without requiring a bus request from that device. This eliminates
the arbitration delay associated with the bus request.
Pipelining Initiating a bus transaction before the current one finishes. This involves running an address tenure
for a new bus transaction before the data tenure for a current bus transaction completes.
Slave The device addressed by the master. The slave is identified in the address tenure and is responsible
for sourcing or sinking the requested data for the master during the data tenure.
Snooping Monitoring addresses driven by a bus master to detect the need for coherency actions.
Split-transaction A transaction with separate request and response tenures.
Tenure The period of bus mastership. For PowerQUICCII, there can be separate address bus tenures and
data bus tenures.
Transaction A complete exchange between two bus devices. A typical transaction is composed of an address
tenure and a data tenure, which may overlap or occur separately from the address tenure. A
transaction can minimally consist of an address tenure alone.
Table8-1. Terminology (continued)
Term Definition