2-47
OVERVIEW OF THE 80C186 FAMILY ARCHITECTURE
Only the single step exception can occur concurrently with another exception. At most, two ex-
ceptions can occur at the same instruction boundary and one of those exceptions must be the sin-
gle step. Single step is a special case; it is discussed on page 2-48. Ignoring single step (for now),
only one exception can occur at any given instruction boundary.
An exception has priority over both NMI and the maskable interrupt. However, a pending NMI
can interrupt the CPU at any valid instruction boundary. Therefore, NMI can interrupt an excep-
tion service routine. If an exception and NMI occur simultaneously, the exception vector is taken,
then is followed immediately by the NMI vector (see Figure 2-28). While the exception has high-
er priority at the instruction boundary, the NMI interrupt service routine is executed first.
Figure 2-28. Simultaneous NMI and Exception
NMI
F = 1
Divide Error
Push PSW, CS, IP
Fetch NMI Vector
Execute NMI
Service Routine
Push PSW, CS, IP
Fetch Divide Error Vector
Execute Divide
Service Routine
IRET
IRET
Divide
A1031-0A
Содержание 80C186XL
Страница 1: ...80C186XL 80C188XL Microprocessor User s Manual...
Страница 2: ...80C186XL 80C188XL Microprocessor User s Manual 1995...
Страница 18: ...1 Introduction...
Страница 19: ......
Страница 27: ......
Страница 28: ...2 Overview of the 80C186 Family Architecture...
Страница 29: ......
Страница 79: ......
Страница 80: ...3 Bus Interface Unit...
Страница 81: ......
Страница 127: ......
Страница 128: ...4 Peripheral Control Block...
Страница 129: ......
Страница 137: ......
Страница 138: ...5 ClockGenerationand Power Management...
Страница 139: ......
Страница 154: ...6 Chip Select Unit...
Страница 155: ......
Страница 178: ...7 Refresh Control Unit...
Страница 179: ......
Страница 193: ......
Страница 194: ...8 Interrupt Control Unit...
Страница 195: ......
Страница 227: ......
Страница 228: ...9 Timer Counter Unit...
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Страница 253: ......
Страница 254: ...10 Direct Memory Access Unit...
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Страница 284: ...11 Math Coprocessing...
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Страница 302: ...12 ONCE Mode...
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Страница 306: ...A 80C186 Instruction Set Additions and Extensions...
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Страница 318: ...B Input Synchronization...
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Страница 322: ...C Instruction Set Descriptions...
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Страница 371: ......
Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
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Страница 396: ...Index...
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