Operator problem

[HenrikOlsson]

Hi,
Which device are you using?
I'm not sure you can access the full TMR1 register pair in one go - even with RD16 enabled. On some devices the 16bit timers are buffered and you need to read the two bytes in the correct order or you'll get the wrong result. On the other hand, you're saying that you can measure and display the period with this very method which I find a bit strange.

You could try something like

DISABLE

intblock:
  INTF=0     'RB0/INT FLG
  T1CON.0 = 1    'Start timer 1

  WHILE INTF=0
@ NOP
  wend

  T1CON.0 = 0 'Stop timer 1

  time.lowbyte = TMR1L
  time.highbyte = TMR1H

  rpm=6000*/10000
  rpm=div32 time

  TMR1L = 0   ' Clear TMR1 so it's ready for next round.
  TMR1H = 0

/Henrik.

[Darrel Taylor]

DIV32 requires that PBP's system variables be loaded with a 32-bit value from a prior 16x16 bit multiplication.
The multiplication has to use at least 1 WORD variable.

But when you specify a multiplication of 2 constants ... the multiplication is done a compile-time as part of the optimization (constant folding).
The system variables never get loaded, because the multiplication was not done at run-time.

The mid-word multiplier is never done at compile-time, even if it has two constants.
It's always done at run-time, and the system variables do get loaded.

And ... TMR1 is declared as a WORD variable in the .pbpinc files.
It's OK to read the entire Timer1 value as long as two conditions are met ... the Timer must be stopped, and RD16 must NOT be set.

[gunayburak]

DIV32 requires that PBP's system variables be loaded with a 32-bit value from a prior 16x16 bit multiplication.
The multiplication has to use at least 1 WORD variable.

But when you specify a multiplication of 2 constants ... the multiplication is done a compile-time as part of the optimization (constant folding).
The system variables never get loaded, because the multiplication was not done at run-time.

The mid-word multiplier is never done at compile-time, even if it has two constants.
It's always done at run-time, and the system variables do get loaded.

And ... TMR1 is declared as a WORD variable in the .pbpinc files.
It's OK to read the entire Timer1 value as long as two conditions are met ... the Timer must be stopped, and RD16 must NOT be set.

You're amazing Darrel ! .. That's such a nice explanation and mind-flashing answer .. Just outta curiosity .. Where do you get such knowledges from ? I mean we can't even get these infos from the compilers reference manual ...

Thank you guys for your prompt answers !

[Darrel Taylor]

Thanks gunayburak,

Everything about PBP is completely transparent.
The libraries (*.lib), macro files (*.mac), the generated assembly language (*.asm) and resulting Listing files (*.LST) are all plain text files that can be viewed with NotePad or similar text editors.

With only 15-years or so of studying those files ... and attempting to solve hundreds of other peoples problems (cause I can't make my own), and you too will know everything there is to know about PicBasic Pro.

Except for about a million things.

[gunayburak]

Yet there is one more problem digging my mind ..
Was I not supposed to get 11 according to the calculation I did at my first post ?
How come I get 3026 ( which is the correct mathematical result and the result I expect to get with only * operand ??

Thanks once again ..

[Darrel Taylor]

Assuming the operations are being done at run-time ...
Internally, both * and */ do the same 16x16 bit multiplication, and the system variables contain the same 32-bit "product".

For the mid-word multiplier, the middle two bytes are then copied to the result variable, in this case rpm.
That result is then discarded and rpm is assigned the value from the DIV32, which used the 32-bit value in the system variables, not the mid-word value.

rpm=6000*/10000  ; <-- This result in rpm is discarded
rpm=div32 time

The same thing applies to the High-Word multiplier **.

[gunayburak]

Thanks to both of you darrel and henrik ...

By the night I will be done with my pid rpm controller unit ...
Thanks to henrik's code which helped me so much with my projects ..
I modified his code to suit my rpm controller

[gunayburak]

Hi,
Which device are you using?
I'm not sure you can access the full TMR1 register pair in one go - even with RD16 enabled. On some devices the 16bit timers are buffered and you need to read the two bytes in the correct order or you'll get the wrong result. On the other hand, you're saying that you can measure and display the period with this very method which I find a bit strange.

You could try something like

DISABLE

intblock:
  INTF=0     'RB0/INT FLG
  T1CON.0 = 1    'Start timer 1

  WHILE INTF=0
@ NOP
  wend

  T1CON.0 = 0 'Stop timer 1

  time.lowbyte = TMR1L
  time.highbyte = TMR1H

  rpm=6000*/10000
  rpm=div32 time

  TMR1L = 0   ' Clear TMR1 so it's ready for next round.
  TMR1H = 0

/Henrik.

That's a nice code too , Thanks Henrik . I am using PIC16F628A and apparently I can reach the entire TMR1 at once ...