Motorola MPC8260 User Manual

MOTOROLA

Chapter 8.  The 60x Bus  

8-5

deÞned by the 60x bus speciÞcation. For more information, see Section 8.5.5, ÒPort Size
Data Bus Transfers and PSDVAL Termination.Ó

The basic functions of the address and data tenures are as follows:

¥

Address tenure

Ñ Arbitration: Address bus arbitration signals are used to request and grant address 

bus mastership.

Ñ Transfer: After a device is granted address bus mastership, it transfers the 

address. The address signals and the transfer attribute signals control the address 
transfer.

Ñ Termination: After the address transfer, the system acknowledges that the 

address tenure is complete or that it must be repeated, signalled by the assertion 
of the address retry signal (ARTRY).

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Data tenure

Ñ Arbitration: After the address tenure begins, the bus device arbitrates for data bus 

mastership.

Ñ Transfer: After the device is granted data bus mastership, it samples the data bus 

for read operations or drives the data bus for write operations.

Ñ Termination: Acknowledgment of a successful data transfer is required after each 

beat in a data transfer. In single-beat transactions, the data termination signals 
also indicate the end of the tenure. In burst or port-size accesses, data termination 
signals indicate the completion of individual beats and, after the Þnal data beat, 
the end of the tenure.

The external bus design permits one device (either the MPC8260 or a bus-attached external
device) to be granted bus mastership at a time. Bus arbitration can be handled either by an

Data Tenure

Arbitration

1- or 4-Beat Transfer

Termination

Next Address Tenure

Independent Address and Data Tenures

Arbitration

Transfer

Termination