Sinclair Basic count seconds...

[firelord]

Is there a way to count seconds in Sinckair Basic;
I want to do some stuff at various intervals and di some waiting.

So far I was using eg PAUSE 100 but when I oress a key it just passes that delay comnand.

Thanks in advance

[catmeows]

There is a system variable called FRAMES, it Is increased every 20 ms

[firelord]

Thanks for the reply.
We can access system variables from normal basic?

[catmeows]

You can use PEEK command to read byte memory.
FRAMES Is three byte value so you read it with code

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10 LET frames=....
20 LET time=PEEK frames+256*PEEK (frames+1)+65536*PEEK(frames+2)
30 PRINT AT 0,0;time,:GOTO 20

Thera two traps:
1) BEEP and tape commands stops time during its execution.
2) since computer changes FRAMES when it wants, on rare occassions you can get wrong time because computer changed FRAMES exactly between evaluating PEEKs. But it can be handled with little extra logic.

I don't remember FRAMES address, please refer Spectrum manual.

[firelord]

ok. Thanks

[p13z]

If you're simply trying to replicate the PAUSE command, but without keypresses cutting it short:
Easiest thing is just to add:

Code: Select all

FOR T=0 TO {arbitrary} : NEXT T

And calibrate the {arbitrary} number to your needs.

[firelord]

If you're simply trying to replicate the PAUSE command, but without keypresses cutting it short:
Easiest thing is just to add:

Code: Select all

FOR T=0 TO {arbitrary} : NEXT T

And calibrate the {arbitrary} number to your needs.

I know that but it seconds counter it s much more secure...

[XTM]

If you add PAUSE 1 to that FOR/NEXT loop, it should take exactly 1 frame (unless BASIC is too slow?) for each cycle. So 50 for 1 second, 500 for 10 seconds etc.

[firelord]

If you add PAUSE 1 to that FOR/NEXT loop, it should take exactly 1 frame (unless BASIC is too slow?) for each cycle. So 50 for 1 second, 500 for 10 seconds etc.

If I press a key won't override the PAUSE command ?

[XTM]

I'm not sure. Guess you could just test it with a loop of 250 which should take 5 seconds. Try running it and stop the time, then run it again but keep a key pressed to see if it makes any difference.

I used to use "PAUSE 1: PAUSE 0" in some of my programs, but I don't remember what the exact reason for it was. I think this can cancel out a key being held before a PAUSE 0?

[+3code]

I've noticed the +3 BASIC interpreter some times ignores PAUSE statements when they are near LOAD/SAVE "m:" commands, but not always, it's a bit buggy.

[firelord]

I used to use "PAUSE 1: PAUSE 0" in some of my programs, but I don't remember what the exact reason for it was. I think this can cancel out a key being held before a PAUSE 0?

I did something like that . I think if you kept a key pressed only the first PAUSE was affected.

[firelord]

I tried this:

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10 FOR T=0 TO 1000 :PAUSE 1: NEXT T

It stops for 20seconds in QAOP (even if I keep a key pressed)

This is interesting to know but my main question is counting seconds so I can :
eg Do A after 10 seconds and do B after 5 more seconds etc...
If I put "IF" inside the FOR loop seconds counting will not work.

[madaxe]

Hi there;

Try this:

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  10 POKE 23672,0
  20 LET n=PEEK (23672)
  30 IF n<50 THEN GOTO 20

In this case 50 means 1 second. Hope you find this usefull

Regards.

[tkfan]

If you add PAUSE 1 to that FOR/NEXT loop, it should take exactly 1 frame (unless BASIC is too slow?) for each cycle. So 50 for 1 second, 500 for 10 seconds etc.

If I press a key won't override the PAUSE command ?

The PAUSE statement do:

1. initialize a counter with value of PAUSE operand;
2. wait for a maskable interrupt;
3. if counter is not 0, decrement it;
4. read keyboard;
5. repeat steps 2-5 until counter is 1 or a valid key has been pressed.

(this is not exactly BASIC ROM PAUSE routine, of course, but the above algorithm has the same behaviour)

When step 2 is executed by the first time, it is unpredictable when a maskable interrupt will be activated, i. e., the delay will take 0-20 ms (milliseconds). Further maskable interrupts will be activated regularly in 20 ms period. Thus, unless FOR/NEXT loop takes more than 20 ms to be executed, PAUSE operand is equivalent to:

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FOR n=1 TO operand: PAUSE 1: NEXT n

but it is not affected by any key press.

[firelord]

Code: Select all

10 FOR T=0 TO 1000 :PAUSE 1: NEXT T

This is identical to my code. But the to 1000 is the difference.in mine the 1000 resulted to about 20seconds.

What I wanted was something like that :
Starttime=(get somehow start time)

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If currenttime-starttime=20 sevonds THEN function1:counter1=counter1+1
If currenttime-starttime=30 sevonds THEN function2

[firelord]

Hi there;

Try this:

Code: Select all

  10 POKE 23672,0
  20 LET n=PEEK (23672)
  30 IF n<50 THEN GOTO 20

In this case 50 means 1 second. Hope you find this usefull

Regards.

(I am a bit slow )
In combination with another thread (viewtopic.php?f=6&t=8404 ) I managed to use a -kind of- reliable counter...

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  5 LET COUNTER=0
  10 POKE 23672,0
  20 LET n=PEEK (23672)
  30 IF n<50 THEN GOTO 20
  35 LET counter=counter+1
  40 PRINT AT 5,0;"Counter:";counter
  150 GOTO 10

I bet that I f I start doing stuff between the counter I will lost the accuracy

[Bedazzle]

I bet that I f I start doing stuff between the counter I will lost the accuracy

Sure. But you can rewrite code a little, and check if value is less that 200 (4 seconds), and by value/50 you can get elapsed seconds.
Why 200? Because after 255 it goes back to zero.

[firelord]

I'm just posting a related post that seems very interesting

viewtopic.php?t=8429