6.17 System Interface Request and Response Protocol

External Request Protocol

An external agent may only issue an external request to the processor when the System interface is in slave state. If the System interface is not already in slave state, the external agent must first negate SysGnt* and then wait for the processor to assert SysRel*. If the System interface is already in slave state, the external agent may issue an external request immediately. The total number of outstanding external requests, including interventions, allocate request numbers, and invalidates, cannot exceed eight.

External requests may be accepted by the processor in adjacent SysClk cycles. External intervention and invalidate requests are considered external coherency requests.

External Intervention Request Protocol

• negating SysCmd[11]
• driving a request number on SysCmd[10:8]
• driving the intervention command on SysCmd[7:5]
• driving the ECC check indication on SysCmd[0]
• driving the target indication on SysAD[63:60]
• driving the physical address on SysAD[39:0]
• asserting SysVal*

Figure 6-20 depicts three external intervention requests. Since the System interface is initially in master state, the external agent must first negate SysGnt* and then wait until the processor relinquishes mastership of the System interface by asserting SysRel*.

Figure 6-20 External Intervention Request Protocol

External Allocate Request Number Request Protocol

• negating SysCmd[11]
• driving a free request number on SysCmd[10:8]
• driving the allocate request number command on SysCmd[7:5]
• asserting SysVal*

Figure 6-21 depicts three external allocate request number requests. Since the System interface is initially in master state, the external agent must first negate SysGnt* and then wait until the processor relinquishes mastership of the System interface by asserting SysRel*.

Figure 6-21 External Allocate Request Number Request Protocol

External Invalidate Request Protocol

• negating SysCmd[11]
• driving a request number on SysCmd[10:8]
• driving the invalidate command on SysCmd[7:5]
• driving the ECC check indication on SysCmd[0]
• driving the target indication on SysAD[63:60]
• driving the physical address on SysAD[39:0]
• asserting SysVal*

Figure 6-22 depicts three external invalidate requests. Since the System interface is initially in master state, the external agent must first negate SysGnt* and then wait until the processor relinquishes mastership of the System interface by asserting SysRel*.

Figure 6-22 External Invalidate Request Protocol

External Interrupt Request Protocol

• negating SysCmd[11]
• driving the special command on SysCmd[7:5]
• driving the interrupt special cause indication on SysCmd[4:3]
• driving the ECC check indication on SysCmd[0]
• driving the target indication on SysAD[63:60]
• driving the Interrupt register write enables on SysAD[20:16]
• driving the Interrupt register values on SysAD[4:0]
• asserting SysVal*

Figure 6-23 depicts three external interrupt requests. Since the System interface is initially in master state, the external agent must first negate SysGnt* and then wait until the processor relinquishes mastership of the System interface by asserting SysRel*.

Figure 6-23 External Interrupt Request Protocol