FWD: Re: Ok, anyone started Contiki 4 AII yet?

[Rob <rsteinmetz@mindspring.com>]

I received this reply by email and am quoting it here by permission.

In comp.sys.apple2 you write:

>Back to the original issue. There is no CLK_TCK function in the Apple
>Library for cc65.


>	1)Is the CLK_TCK function necessary?


CLK_TCK would be 60 on most Apple // systems.


>	2)What is it used for?


It is so you can scale the value of functions that count in ticks.


>	3)Is it something which can be generated on a stock Apple ][?


You would need to add a source of interrupts (eg Mouse II card) and set
up an IRQ handler to count VBL pulses.


>IIRC the Apple ][ generates its timing in an unusual and Woz way,
>without a crystal. Can CLK_TCK be generated in the same way?


The Apple II does have a crystal - 14.31818 MHz if I recall it correctly.
It is the CPU clock that is more complicated with its stretched cycle 1 
in 65.
-- David Wilson School of IT & CS, Uni of Wollongong, Australia