Motorola MPC8260 - Manual (Page 237)

MOTOROLA Chapter 8. The 60x Bus 8-5
Part III. The Hardware Interface
deÞned by the 60x bus speciÞcation. For more information, see Section 8.5.5, ÒPort Size
Data Bus Transfers and PSDVAL Termination.Ó
Figure 8-3. Basic Transfer Protocol
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).
¥ 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.
8.3.1 Arbitration Phase
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