Re: [avr-libc-dev] _delay_us() - Documentation for maximum possible delay

[Joerg Wunsch]

As Boyapati, Anitha wrote:

> The above link says, the maximal possible delay for _delay_us() is
> 768 us / F_CPU in MHz. However, as per the below computation, it
> should be 765us.  (Max value of _ticks when it is of uint8_t type is
> 255.)

No, the max value is 256, even though it is represented as 0. ;-)

> Also, any reason why _ticks is chosen to be uint8_t type (but not
> uint16_t or uint32_t)?

Because the underlying _delay_loop_1 uses an 8-bit value.
_delay_loop_2 uses a 16-bit value, and that's what _delay_ms() is
based on.  That doesn't imply you could not achieve shorter delays,
since e.g. _delay_ms(0.8) is completely acceptable.  It's just the
increased granularity of _delay_loop_2 makes it preferrable for longer
delay.

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)