Delay definition is - the act of postponing, hindering, or causing something to occur more slowly than normal: the state of being delayed. How to use delay in a sentence. Synonym Discussion of delay. Many programming languages have a sleep function that will delay a program’s execution for a given number of seconds. This functionality is absent from JavaScript, however, owing to its.
Macros | |
#define | F_CPU 1000000UL |
Functions | |
void | _delay_ms (double __ms) |
void | _delay_us (double __us) |
Detailed Description
Delayed Gratification
- Note
- As an alternative method, it is possible to pass the F_CPU macro down to the compiler from the Makefile. Obviously, in that case, no
#define
statement should be used.
The functions in this header file are wrappers around the basic busy-wait functions from <util/delay_basic.h>. They are meant as convenience functions where actual time values can be specified rather than a number of cycles to wait for. The idea behind is that compile-time constant expressions will be eliminated by compiler optimization so floating-point expressions can be used to calculate the number of delay cycles needed based on the CPU frequency passed by the macro F_CPU.
- Note
- In order for these functions to work as intended, compiler optimizations must be enabled, and the delay time must be an expression that is a known constant at compile-time. If these requirements are not met, the resulting delay will be much longer (and basically unpredictable), and applications that otherwise do not use floating-point calculations will experience severe code bloat by the floating-point library routines linked into the application.
The functions available allow the specification of microsecond, and millisecond delays directly, using the application-supplied macro F_CPU as the CPU clock frequency (in Hertz).
Macro Definition Documentation
CPU frequency in Hz.
The macro F_CPU specifies the CPU frequency to be considered by the delay macros. This macro is normally supplied by the environment (e.g. from within a project header, or the project's Makefile). The value 1 MHz here is only provided as a 'vanilla' fallback if no such user-provided definition could be found.
In terms of the delay functions, the CPU frequency can be given as a floating-point constant (e.g. 3.6864E6 for 3.6864 MHz). However, the macros in <util/setbaud.h> require it to be an integer value.
Function Documentation
Perform a delay of __ms
milliseconds, using _delay_loop_2().
The macro F_CPU is supposed to be defined to a constant defining the CPU clock frequency (in Hertz).
The maximal possible delay is 262.14 ms / F_CPU in MHz.
When the user request delay which exceed the maximum possible one, _delay_ms() provides a decreased resolution functionality. In this mode _delay_ms() will work with a resolution of 1/10 ms, providing delays up to 6.5535 seconds (independent from CPU frequency). The user will not be informed about decreased resolution.
If the avr-gcc toolchain has __builtin_avr_delay_cycles() support, maximal possible delay is 4294967.295 ms/ F_CPU in MHz. For values greater than the maximal possible delay, overflows results in no delay i.e., 0ms.
Conversion of __ms
into clock cycles may not always result in integer. By default, the clock cycles rounded up to next integer. This ensures that the user gets at least __ms
microseconds of delay.
Alternatively, by defining the macro __DELAY_ROUND_DOWN__
, or __DELAY_ROUND_CLOSEST__
, before including this header file, the algorithm can be made to round down, or round to closest integer, respectively.
- Note
The implementation of _delay_ms() based on __builtin_avr_delay_cycles() is not backward compatible with older implementations. In order to get functionality backward compatible with previous versions, the macro '__DELAY_BACKWARD_COMPATIBLE__'
must be defined before including this header file. Also, the backward compatible algorithm will be chosen if the code is compiled in a freestanding environment (GCC option -ffreestanding
), as the math functions required for rounding are not available to the compiler then.
Perform a delay of __us
microseconds, using _delay_loop_1().
The macro F_CPU is supposed to be defined to a constant defining the CPU clock frequency (in Hertz).
The maximal possible delay is 768 us / F_CPU in MHz.
If the user requests a delay greater than the maximal possible one, _delay_us() will automatically call _delay_ms() instead. The user will not be informed about this case.
If the avr-gcc toolchain has __builtin_avr_delay_cycles() support, maximal possible delay is 4294967.295 us/ F_CPU in MHz. For values greater than the maximal possible delay, overflow results in no delay i.e., 0us.
Conversion of __us
into clock cycles may not always result in integer. By default, the clock cycles rounded up to next integer. This ensures that the user gets at least __us
microseconds of delay.
Delayed Justice
Alternatively, by defining the macro __DELAY_ROUND_DOWN__
, or __DELAY_ROUND_CLOSEST__
, before including this header file, the algorithm can be made to round down, or round to closest integer, respectively.
- Note
The implementation of _delay_ms() based on __builtin_avr_delay_cycles() is not backward compatible with older implementations. In order to get functionality backward compatible with previous versions, the macro __DELAY_BACKWARD_COMPATIBLE__
must be defined before including this header file. Also, the backward compatible algorithm will be chosen if the code is compiled in a freestanding environment (GCC option -ffreestanding
), as the math functions required for rounding are not available to the compiler then.
146 results
- DELAY - CHICKASAW INDIAN NATION 1899Doug Miller 9/08/10
- John Thomas DeLayColin Ovenston 12/08/10
- Jessie Lee Delay Oglethorpe Co Gajeff gilbert 1/15/11
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- Re: Jessie Lee Delay Oglethorpe Co GaA C 6/19/11
- Re: Jessie Lee Delay Oglethorpe Co Ga
- Margarette A. DeLayJolene Strausbaugh 4/10/09
- daniel Delaysharon bowden 1/25/09
- Re: daniel Delay
- Re: daniel Delaysharon bowden 4/23/09
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- Re: daniel DelayDoug Miller 3/14/10
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- Re: DeLay Genealogical FilesNancy Kauth 7/03/12
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- Zell DeLay 2nd bookKarin DeLay Scott 9/17/12
- Sarah Delay md James Williams in 1792Toby Williams 12/29/12
- David Delay and Mary Garrett family of IndianaMary Martin 8/01/09
- Re: David Delay and Mary Garrett family of Indiana
- Re: David Delay and Mary Garrett family of IndianaMary Martin 12/30/09
- Re: David Delay and Mary Garrett family of IndianaLorraine Doty 4/10/10
- Re: David Delay and Mary Garrett family of Indiana
- Re: David Delay and Mary Garrett family of Indiana
- Re: David Delay and Mary Garrett family of Indiana