BUS INTERFACE UNIT
3-42
Figure 3-35. Refresh Request During HOLD
The device requesting a bus hold must be able to detect a HLDA pulse that is one clock in dura-
tion. A bus lockup (hang) condition can result if the requesting device fails to detect the short
HLDA pulse and continues to wait for HLDA to be asserted while the BIU waits for HOLD to be
deasserted. The circuit shown in Figure 3-36 can be used to latch HLDA.
HLDA
CLKOUT
HOLD
NOTES:
1. HLDA is deasserted, signaling need to run refresh bus cycle.
2. External bus master terminates use of the bus.
3. HOLD deasserted.
4. Hold may be reasserted after one clock.
5. BIU runs refresh cycle.
1
4
3
AD15:0
DEN
A19:16
RD, WR,
BHE, S2:0
DT/R,
LOCK
5
5
2
A1061-0A
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...
Страница 229: ......
Страница 253: ......
Страница 254: ...10 Direct Memory Access Unit...
Страница 255: ......
Страница 283: ......
Страница 284: ...11 Math Coprocessing...
Страница 285: ......
Страница 302: ...12 ONCE Mode...
Страница 303: ......
Страница 306: ...A 80C186 Instruction Set Additions and Extensions...
Страница 307: ......
Страница 318: ...B Input Synchronization...
Страница 319: ......
Страница 322: ...C Instruction Set Descriptions...
Страница 323: ......
Страница 371: ......
Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
Страница 373: ......
Страница 396: ...Index...
Страница 397: ......