MPC8280 datasheet(278/1386 Pages) FREESCALE

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The 60x Bus

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

8-2

Freescale Semiconductor

8.2

Bus Configuration

The 60x bus supports separate bus configurations for internal masters and external bus masters.

•

Single-MPC8280 bus mode connects external devices by using only the memory controller. This

is described in Section 8.2.1, “Single-MPC8280 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 MPC8280 can be connected in these two

configurations.

8.2.1

Single-MPC8280 Bus Mode

In single-MPC8280 bus mode, the MPC8280 is the only bus device in the system. The internal memory

controller controls all devices on the external pins. Figure 8-1 shows the signal connections for

single-MPC8280 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 MPC8280, 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.

Table 8-1. Terminology (continued)

Term

Definition

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