tweaks to readme

Author: Elliot Williams

code/README.md

@@ -10,9 +10,9 @@ I've even included the .hex files if you just want to run it, and don't want to
 
 There's one trick: I wanted sub-microsecond pulses for experimentation, and the AVR's `_us_delay` function has one microsecond as the lower bound.  The solution is to tell the delay function that we're running the CPU at 1 MHz, and then actually run the CPU at 8 MHz.  (If you want more resolution, you can play around with other combinations.)
 
-So, in the Makefile, you'll find `F_CPU` defined as 1 MHz, and in the code you'll see that I've set the clock prescaler to 1, which means the chip is running at the full 8 MHz.  If you want to play around with other ratios, define `F_CPU` to be even slower.  
+So, in the Makefile, you'll find `F_CPU` defined as 1 MHz, and in the code you'll see that I've set the clock prescaler to 1, which means the chip is running at the full 8 MHz. 
 
 But caveat: the routines for calculating the baud rates on the serial hardware also rely on `F_CPU` .  If you're using that peripheral, you'll need to adjust things accordingly.  
 
-Anyway, if you want a nominal 1 us pulse, you'll need to call `_delay_us(8)`.  That's all there is to it.
+Anyway, if you want a nominal 1 us pulse, you'll need to call `_delay_us(8)`.  There's some function-call overhead that makes this not work out exactly, so check out the pulses on a scope if you've got one.  Otherwise, that's all there is to it.