8XC251SA, SB, SP, SQ USER’S MANUAL
6-12
Figure 6-7. Response Time Example #2
6.7.2.2
Computation of Worst-case Latency With Variables
Worst-case latency calculations assume that the longest 8XC251Sx instruction used in the pro-
gram must fully execute prior to a context switch. The instruction execution time is reduced by
one state with the assumption the instruction state overlaps the request state (therefore, 16-bit
DIV is 21 state times - 1 = 20 states for latency calculations). The calculations add fixed and vari-
able interrupt times (see Table 6-6) to this instruction time to predict latency. The worst-case la-
tency (both fixed and variable times included) is expressed by a pseudo-formula:
OSC
State Time
INT0#
Sample INT0#
Response Time = 4
Ten State
Instruction
Request
Push PC
A4154-02
FIXED_TIME
VARIABLES
LONGEST_INSTRUCTION
+
+
MAXIMUM LATENCY PREDICTION
=
Содержание 8XC251SA
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Страница 3: ...May 1996 8XC251SA 8XC251SB 8XC251SP 8XC251SQ Embedded Microcontroller User s Manual...
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Страница 19: ...1 Guide to This Manual...
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Страница 31: ...2 Architectural Overview...
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Страница 41: ...3 Address Spaces...
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Страница 63: ...4 Device Configuration...
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Страница 81: ...5 Programming...
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Страница 103: ...6 Interrupt System...
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Страница 121: ...7 Input Output Ports...
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Страница 133: ...8 Timer Counters and Watchdog Timer...
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Страница 153: ...9 Programmable Counter Array...
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Страница 171: ...10 Serial I O Port...
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Страница 187: ...11 Minimum Hardware Setup...
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Страница 197: ...12 Special Operating Modes...
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Страница 207: ...13 External Memory Interface...
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Страница 239: ...14 Programming and Verifying Nonvolatile Memory...
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Страница 251: ...A Instruction Set Reference...
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Страница 391: ...B Signal Descriptions...
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Страница 401: ...C Registers...
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Страница 437: ...Glossary...
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Страница 447: ...Index...
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