BUS INTERFACE UNIT
3-32
Figure 3-28. Returning to HALT After a DMA Bus Cycle
3.5.6
Exiting HALT
An NMI or any unmasked INTn interrupt causes the BIU to exit HALT. The first bus operations
to occur after exiting HALT are read cycles to reload the CS:IP registers. Figure 3-29 shows how
the HALT bus state is exited when an NMI or INTn occurs.
T1
T2
T3
T4
T1
T2
T3
TI
CLKOUT
AD15:0
[AD7:0]
TI
TI
ALE
[A15:8]
A19:16
Valid Status
Valid Status
Note
Addr
8H
8H
Note
Valid
Valid
NOTE: Drives previous bus cycle value.
TI
BHE
[RFSH=1]
S2:0
T4
Address
Note
Address
Addr
Addr
Valid Data
Addr
A1515-0A
Summary of Contents for 80C186XL
Page 1: ...80C186XL 80C188XL Microprocessor User s Manual...
Page 2: ...80C186XL 80C188XL Microprocessor User s Manual 1995...
Page 18: ...1 Introduction...
Page 19: ......
Page 27: ......
Page 28: ...2 Overview of the 80C186 Family Architecture...
Page 29: ......
Page 79: ......
Page 80: ...3 Bus Interface Unit...
Page 81: ......
Page 127: ......
Page 128: ...4 Peripheral Control Block...
Page 129: ......
Page 137: ......
Page 138: ...5 ClockGenerationand Power Management...
Page 139: ......
Page 154: ...6 Chip Select Unit...
Page 155: ......
Page 178: ...7 Refresh Control Unit...
Page 179: ......
Page 193: ......
Page 194: ...8 Interrupt Control Unit...
Page 195: ......
Page 227: ......
Page 228: ...9 Timer Counter Unit...
Page 229: ......
Page 253: ......
Page 254: ...10 Direct Memory Access Unit...
Page 255: ......
Page 283: ......
Page 284: ...11 Math Coprocessing...
Page 285: ......
Page 302: ...12 ONCE Mode...
Page 303: ......
Page 306: ...A 80C186 Instruction Set Additions and Extensions...
Page 307: ......
Page 318: ...B Input Synchronization...
Page 319: ......
Page 322: ...C Instruction Set Descriptions...
Page 323: ......
Page 371: ......
Page 372: ...D Instruction Set Opcodes and Clock Cycles...
Page 373: ......
Page 396: ...Index...
Page 397: ......