diff options
Diffstat (limited to 'openpicc/timer-design.txt')
| -rw-r--r-- | openpicc/timer-design.txt | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/openpicc/timer-design.txt b/openpicc/timer-design.txt index 392d537..b56ded1 100644 --- a/openpicc/timer-design.txt +++ b/openpicc/timer-design.txt @@ -44,8 +44,10 @@ tc_cdiv: XC1=TCLK1 (in), TIOB0 (out), TIOA0 (out), XC2=TCLK2 (in) RA = 1, RB = 1 + divider/2, RC = divider i.o.w: when CV = 0 (either through swtrg or through RC compare) then TIOA0 and TIOB0 are clear - TIOA0 is set on RA compare (at CV=1), is connected to XC2 (through TCLK2) and therefore triggers the external event which sets TIOB0 - TIOB0 is cleared at RB compare (at CV=1+divider/2) + TIOA0 is set on RA compare (at CV=1+phase), is connected to XC2 (through TCLK2) and therefore triggers the external event which sets TIOB0 + TIOB0 is cleared at RB compare (at CV=1+divider/2+phase) + that means: Compare A sets TIOB and Compare B clears TIOB, Compare C is fixed at the divisor value, Compare A and B are divisor/2 apart, yielding an exact 50% duty cycle with a variable phase shift (offset from CV=0) + this trick is necessary because TIO{A,B} can't be directly affected by Compare {B,A}, so when using only one TIO you can either get a fixed duty cycle with zero offset compared to CV=0, or a variable offset yielding a variable duty cycle tc_fdt: TIOA2 (out), TIOB2 (in), XC1=TCLK1 (in) TC2 enabled |