different software times, impossible?

[richard]

what's the lowest possible increment in uS units of the two other timers with 20mhz quartz?

i think thats the wrong question

1. first thing is what time intervals are required to toggle the output at to achieve for the given number of pulses in the time frame
2. are they all possible within the available timer resolution ? how many pulses do you really need ? steps of 5 10, 50 ,1 ,2 ?
3. what method will be fast enough to toggle the output and count the pulses too .ie an isr or a fast loop to monitor timer overflows

PULSES TOGGLES PERIOD uS
100 199 1204.52
101 201 1192.54
150 299 801.67
200 399 600.75
250 499 480.36
300 599 400.17
350 699 342.92
400 799 300.00
450 899 266.63
500 999 239.94
550 1099 218.11
599 1197 200.25
600 1199 199.92

[lutherblisset]

hi richard, to match the x pulses (1666hz) for the y pulses i need to set a range from 500us (250high+250low) to 7500us (3750high+3750low) the increment can be 50us. For your 3rd question i need your help....

[richard]

if you go down that path then

toggle /time
pulses

250

479

300

399

350

342

400

299

450

266

500

239

550

217

600

199

650

184

700

171

750

159

800

149

850

141

900

133

950

126

1000

119

1050

114

1100

108

1150

104

1200

99

1250

95

1300

92

1350

88

1400

85

1450

82

1500

79

1550

77

1600

74

1650

72

1700

70

1750

68

1800

66

1850

64

1900

63

1950

61

2000

59

2050

58

2100

57

2150

55

2200

54

2250

53

2300

52

2350

51

2400

49

2450

48

2500

47

2550

47

2600

46

2650

45

2700

44

2750

43

2800

42

2850

42

2900

41

2950

40

3000

39

3050

39

3100

38

3150

38

3200

37

3250

36

3300

36

3350

35

3400

35

3450

34

3500

34

3550

33

3600

33

3650

32

3700

32

3750

31

then :-
1. your range is 31 to 479 pulses nothing like the 100-600 initially specified
2. not every period produces a different pulse count
3. pulses will not always finish synchronously within the 400 pulse stream
4. the pulse count varies in a non-linear manner

[lutherblisset]

hi richard, i understand. The 31-479 possible pulses of y for every 400 pulses of x are for me necessary, it's impossible for me to change those three parameters. i know it's a problem of "times", they are like two "digital gears" and i must find the way to match the reciprocal "teeth". The frequency of x now is 1666 hz (240.000uS) but the x motor accept other frequencies too. More difficult for me is understand interrupts, overflow, ticks, to find my way and the possible solution

[richard]

More difficult for me is understand interrupts, overflow, ticks, to find my way and the possible solution

the forum is crammed full of examples

search "blinky" to see some relevant ideas

perhaps if you provide more detailed information about what you are trying to achieve preferably with some examples of the code that you have tried , more help would be offered.
as it stands your goal is a mystery and worse still the goalposts seem to keep moving . speculation wastes everyone time and patience.
(I'm thinking now that an electronically variable gearbox might be your target , if so this approach is not going to work) but that's just speculation

[lutherblisset]

anyway the pwm (the only way to have two pulses on different ports of a pic at the same time) it's not good for me cause i work with stepper motors and i have to define closed number of steps, not frequencies. Cause i must define fix numbers, not number of pulses for second. I can't tell the pic to count until 9600 on a port and to count until 120000 on another port at the same time (the quartz of course) its impossible.

[amgen]

from what you have described so far, it may be easier than it seems to implement this..... maybe.
1, you have to use timer interrupt at 50micro seconds..... the highest common value for both times
2, you implement a while/wend loop with block of code for main X....hi/low and total run ... and block of code for Y .... with values you calculated
3, using counters in blocks to toggle pins and exit while when pulses/count are reached
4, outside of while blocks to get/calculate new Y's.... do other stuff then startup a new round of pulses
5, the constraint is all the code inside blocks have to be less than 50micro seconds..... at 20 MHZ should able to do about 100 to 200 instructions in 50micro seconds