6.16 System Interface Arbitration

Uniprocessor System

Figure 6-6 shows how the System interface arbitration signals are used in a uniprocessor system. Note that this same configuration would be used in a multiprocessor system using dedicated external agents.

Figure 6-6 Arbitration Signals for Uniprocessor System

Figure 6-7 is an example of the operation of the System interface arbitration in a uniprocessor system. The Master row in the following figures indicates which device is driving the System interface bidirectional signals (P0 and EA in
Figure 6-7). When this row contains a dash (-), as shown in Cycle 12 of Figure 6-7, mastership of the System interface is changing and no device is driving the System interface bidirectional signals for this one dead SysClk cycle.

The external agent generally asserts the SysGnt* signal, which allows the processor to issue requests at any time.

When the external agent needs to return an external data response, it negates SysGnt* for a minimum of one cycle, waits for the processor to assert SysRel*, and then begins driving the System interface bus after one dead SysClk cycle.

Figure 6-7 Arbitration Protocol for Uniprocessor System

Copyright 1996, 1997, MIPS Technologies, Inc. -- 09 DEC 96

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