3-43
BUS INTERFACE UNIT
Figure 3-36. Latching HLDA
The removal of HOLD must be detected for at least one clock cycle to allow the BIU to regain
the bus and execute a refresh bus cycle. Should HOLD go active before the refresh bus cycle is
complete, the BIU will release the bus and generate HLDA.
3.7.2
Exiting HOLD
Figure 3-37 shows the timing associated with exiting the bus hold state. Normally a bus operation
(e.g., an instruction prefetch) occurs just after HOLD is released. In a 16-bit bus system, the upper
half of the bus (D15:8) floats.
A1535-0A
D
Q
Latched HLDA
RESET
HOLD
CLR
HLDA
PRE
+5
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: ......