INTERRUPTS
11-38
11.9.4
Maximum Interrupt Latency
In real-time applications, worst-case interrupt latency must be considered for critical handling of
external events. For example, an interrupt from a mechanical subsystem may need service to
calculate servo loop parameters to maintain directional control. Determining worst-case latency
depends on knowledge of the processor’s instruction mix and operating environment as well as the
interrupt controller configuration. Excluding certain very long, uninterruptable instructions from
critical sections of code reduces worst-case interrupt latency to levels approaching the base latency.
The following tables present worst-case interrupt latencies based on possible execution of
divo
(r15
destination),
divo
(r3 destination),
calls
or
flushreg
instructions or software interrupt detection. The
assumptions for these tables are the same as for
Table 11-8
, except for instruction execution. It is
also assumed that the instructions are already in the cache and that tracing is disabled.
Table 11-4. Worst-Case Interrupt Latency Controlled by divo to Destination r15
Interrupt Type
Detection
Option
Vector
Caching
Enabled
Worst
80960JA/JF
Latency
(Bus Clocks)
Worst
80960JD
Latency
(Bus Clocks)
Worst
80960JT (3x)
Latency
(Bus Clocks)
NMI
Fast
Yes
42
23.5
16.7
Debounced
Yes
46
26
20.3
Dedicated Mode
XINT[7:0], TINT[1:0]
Fast
Yes
45
23.5
17
No
45+a
23.5+b
17+c
Debounced
Yes
49
27.5
22.3
No
51+a
27.5+b
22.3+c
Expanded Mode
XINT[7:0], TINT[1:0]
Debounced
Yes
50
27.5
21
No
51+a
27.5+b
21+c
NOTES:
a = MAX (0,N - 11)
b = MAX (0,N - 5)
c = MAX (0, N-4.7)
where “N” is the number of bus cycles needed to perform a word load.
Summary of Contents for i960 Jx
Page 1: ...Release Date December 1997 Order Number 272483 002 i960 Jx Microprocessor Developer s Manual ...
Page 24: ......
Page 25: ...1 INTRODUCTION ...
Page 26: ......
Page 35: ...2 DATA TYPES AND MEMORY ADDRESSING MODES ...
Page 36: ......
Page 46: ......
Page 47: ...3 PROGRAMMING ENVIRONMENT ...
Page 48: ......
Page 73: ...4 CACHE AND ON CHIP DATA RAM ...
Page 74: ......
Page 85: ...5 INSTRUCTION SET OVERVIEW ...
Page 86: ......
Page 111: ...6 INSTRUCTION SET REFERENCE ...
Page 112: ......
Page 233: ...7 PROCEDURE CALLS ...
Page 234: ......
Page 256: ......
Page 257: ...8 FAULTS ...
Page 258: ......
Page 291: ...9 TRACING AND DEBUGGING ...
Page 292: ......
Page 309: ...10 TIMERS ...
Page 310: ......
Page 324: ......
Page 325: ...11 INTERRUPTS ...
Page 326: ......
Page 369: ...12 INITIALIZATION AND SYSTEM REQUIREMENTS ...
Page 370: ......
Page 412: ......
Page 413: ...13 MEMORY CONFIGURATION ...
Page 414: ......
Page 429: ...14 EXTERNAL BUS ...
Page 430: ......
Page 468: ......
Page 469: ...15 TEST FEATURES ...
Page 470: ......
Page 493: ...A CONSIDERATIONS FOR WRITING PORTABLE CODE ...
Page 494: ......
Page 502: ......
Page 503: ...B OPCODES AND EXECUTION TIMES ...
Page 504: ......
Page 515: ...C MACHINE LEVEL INSTRUCTION FORMATS ...
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Page 523: ...D REGISTER AND DATA STRUCTURES ...
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Page 550: ......
Page 551: ...GLOSSARY ...
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Page 561: ...INDEX ...
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