AMD AMD-K6-2/500AFX Data Sheet - Page 182

Interrupt Acknowledge, Table 29., Interrupt Acknowledge Operation Definition

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AMD-K6®-2 Processor Data Sheet Preliminary Information 21850J/0-February 2000 Interrupt Acknowledge In response to recognizing the system's maskable interrupt (INTR), the processor drives an interrupt acknowledge cycle at the next instru cti on boundary. Dur ing an inter rupt acknowledge cycle, the processor drives a locked pair of read cycles as shown in Figure 71. The first read cycle is not functional, and the second read cycle returns the interrupt number on D[7:0] (00h-FFh). Table 29 shows the state of the signals during an interrupt acknowledge cycle. Table 29. Interrupt Acknowledge Operation Definition Processor Outputs D/C# M/IO# W/R# BE[7:0]# A[31:3] D[63:0] First Bus Cycle Low Low Low EFh 0000_0000h (ignored) Second Bus Cycle Low Low Low FEh (low byte enabled) 0000_0000h Interrupt number expected from interrupt controller on D[7:0] The system logic can drive INTR either synchronously or asynchronously. If it is asserted asynchronously, it must be asserted for a minimum pulse width of two clocks. To ensure it is recognized, INTR must remain asserted until an interrupt acknowledge sequence is complete. 162 Bus Cycles Chapter 5

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162
Bus Cycles
Chapter 5
AMD-K6
®
-2 Processor Data Sheet
21850J/0—February 2000
Preliminary Information
Interrupt
Acknowledge
In response to recognizing the system’s maskable interrupt
(INTR), the processor drives an interrupt acknowledge cycle at
the next instruction boundary. During an interrupt
acknowledge cycle, the processor drives a locked pair of read
cycles as shown in Figure 71. The first read cycle is not
functional, and the second read cycle returns the interrupt
number on D[7:0] (00h–FFh). Table 29 shows the state of the
signals during an interrupt acknowledge cycle.
The system logic can drive INTR either synchronously or
asynchronously. If it is asserted asynchronously, it must be
asserted for a minimum pulse width of two clocks. To ensure it
is recognized, INTR must remain asserted until an interrupt
acknowledge sequence is complete.
Table 29.
Interrupt Acknowledge Operation Definition
Processor Outputs
First Bus Cycle
Second Bus Cycle
D/C#
Low
Low
M/IO#
Low
Low
W/R#
Low
Low
BE[7:0]#
EFh
FEh (low byte enabled)
A[31:3]
0000_0000h
0000_0000h
D[63:0]
(ignored)
Interrupt number expected from interrupt
controller on D[7:0]