3-21
BUS INTERFACE UNIT
T
OE
, T
ACC
and T
CE
define the maximum data access requirements for the memory device. These
device parameters must be less than the value calculated in the equation column. An equal to or
greater than result indicates that wait states must be inserted into the bus cycle.
T
DF
determines the maximum time the memory device can float its outputs before the next bus
cycle begins. A T
DF
value greater than the equation result indicates a buffer fight. A buffer fight
means two (or more) devices are driving the bus at the same time. This can lead to short circuit
conditions, resulting in large current spikes and possible device damage.
T
RHAX
cannot be lengthened (other than by slowing the clock rate). To resolve a buffer fight con-
dition, choose a faster device or buffer the AD bus (see “Buffering the Data Bus” on page 3-34).
Figure 3-19. Typical Read Bus Cycle
ALE
S2:0
A19:16
CLKOUT
T1
T2
T3
T4
A18:16 = 0, A19=Valid Status
A15:8
RFSH
Valid
A15:0
[AD7:0]
RD
DT/R
DEN
BHE
Status Valid
Address Valid
Data
Valid
Address
Valid
A1046-0A
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: ......