Et a quoi correspond les bits du port 0x600015 et 0x600017. Et sont t'il dangereux à utiliser pour la calculatrice?
$600015 RW ($1B)
:7 Master disable timer interrupts (level 1, 3 and 5)
:6 - (HW2: ?)
:5-4 Increment rate of $600017
%00: OSC2/2^5
%01: OSC2/2^9 (AMS default)
%10: OSC2/2^12
%11: OSC2/2^18
:3 Enable incrementing of $600017
:2 Trigger interrupt level 3 at OSC2/2^19 (~1 Hz on HW2)
:1 OSC2 (and OSC3?) enable (bit clear means oscillator stopped!)
:0 LCD controller DMA enable, LCD blank ("white") if =0
This bit is only examined by the hardware at the start of
each frame.
HW1: The DMA steals ~10% of the CPU bus bandwidth.
$600017 RW ($B2 = 257-79 for HW1, $CC = 257-53 for HW2)
:7-0 READ: Read the current value
WRITE: Set the initial (and current) value for the timer
The timer value is incremented at the rate specified at $600015 and
triggers interrupt level 5 when it "overflows" to $00. The next
increment forces the timer to reload the initial value. The
count sequence looks like this:
value, value+1, ..., $FF, $00 (interrupt!), value, value+1, ...
To trigger an interrupt every 'n'th increment, write '257-n' to
this register.
