Instant Interrupts - Revisited

**Darrel Taylor** · - 7th February 2006, 08:37

So far I've shown one interrupt source being used at a time, but as I said in the first post, you can easily service Multiple Interrupt Sources.   So what if we wanted to join the previous 3 examples into one program.   NOT a problem!

To add more interrupt "Handlers", simply add them to the INT_LIST, and create a subroutine for them.

Since both the Blinky Light, and Elapsed Timer used TMR1, lets move the Blinky Light over to TMR0. Elapsed will still use TMR1.

Code:

LED1   VAR  PORTD.0
LED2   VAR  PORTD.1

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts
INCLUDE "Elapsed_INT.bas"    ' Elapsed Timer Routines

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
        INT_Handler   TMR0_INT,  _ToggleLED2,   PBP,  yes
        INT_Handler   TMR1_INT,  _ClockCount,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor

    INT_ENABLE   INT_INT     ; enable external (INT) interrupts
    INT_ENABLE  TMR0_INT     ; enable Timer 0 interrupts
    INT_ENABLE  TMR1_INT     ; Enable Timer 1 Interrupts  
ENDASM

OPTION_REG = OPTION_REG & $80 | 1  ; Set TMR0 Prescaler to 256, leave RBPU alone
GOSUB ResetTime              ' Reset Time to  0d-00:00:00.00
GOSUB StartTimer             ' Start the Elapsed Timer

Main:
    IF SecondsChanged = 1 THEN  
       SecondsChanged = 0
       LCDOUT $FE,$C0, DEC Days,"d-",DEC2 Hours,":",DEC2 Minutes,":",DEC2 Seconds
    ENDIF
GOTO Main

'---[INT - interrupt handler]---------------------------------------------------
ToggleLED1:
     TOGGLE LED1
@ INT_RETURN

'---[TMR0 - interrupt handler]-------------------------------(Blinky Light)------
T0Count  VAR WORD
ToggleLED2:
    T0Count = T0Count + 1
    IF T0Count = 512 THEN T0Count = 0 : TOGGLE LED2
@ INT_RETURN

<font size=-2>Code Size = 711 Words</font>

Now we have all three interrupt sources working together in the same program.

LED1 responds to the external INT
LED2 flashes, timed by TMR0
and, the elapsed timer is maintained via TMR1

And, all of this is happening behind the scenes of your normal PBP program.

**Darrel Taylor** · - 10th February 2006, 11:55

</td><td>The Instant Interrupt System consists of several "Layers".

The Bottom Layer is "DT_INTS-14.bas". This file contains everything required to use Interrupts at the ASM level.   It handles all of the "Context Saving/Restoring", detects which interrupt has been triggered, and calls the appropriate "User Routine".

The next layer up is created from the INT_LIST macro you define in the program.   It defines the Interrupt sources to use and the corresponding subroutines that will be called.   They can be either simple subroutines, or complete "Modules" in a separate Include file, like the Elapse Timer.   Up to 14 separate INT_Handler's can be in the LIST.

And, the Top Layer is the normal PBP program that runs in the foreground.

If Basic Laguage interrupts are not being used, then DT_INTS-14.bas is the only file you need to include.</td></tr></table>Here's another example of a Blinky Light program using TMR1 with an Assembly Language Interrupt handler

Code:

LED1   VAR  PORTD.0
LOW  LED1                    ; Set to Output Low

INCLUDE "DT_INTS-14.bas"     ; Base Interrupt System

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,   ToggleLED1,   ASM,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor

    INT_ENABLE  TMR1_INT     ; Enable Timer 1 Interrupts  
ENDASM

T1CON = $31                  ; Prescaler=8, TMR1ON

Main:
    PAUSE 1
GOTO Main

'---[TMR1_INT - interrupt handler]------------------------------------------
ASM
ToggleLED1
    btfsc  _LED1
    goto   $+3
    bsf    _LED1
    goto   $+2
    bcf    _LED1
    INT_RETURN
ENDASM

<font size=-3>Code Size = 104 Words</font>

Notice that the INT_Handler's Type is ASM, and the Label does not have an underscore before it.<hr><table cellpadding=6><tr><td>

</td><td valign=top>By using this type of Layering scheme. It allows us more flexability, depending on the type of interrupt we want to use.   If we want to add Basic Language Handlers, all we need to do is Include "ReEnterPBP.bas", and it will insert another Layer in-between the Base and the Handlers.

With this layer included, you can have any combination of ASM and PBP interrupts in the same program</td></tr></table>
<br>

**Darrel Taylor** · - 10th February 2006, 12:51

October 05, 2002 was a good day.   Because that's the day that Tim Box released his "INT_CTRL.pbp" program.   The original "Instant Interrupts"

Tim had discovered that the only reason you couldn't use Basic statements in a normal interrupt, was because the PBP system variables currently being used by the statement that got interrupted, would be overwritten by the Basic statements in the interrupt routine.   And that, all you have to do is save the state of the system vars at the start of the interrupt, and restore them back to the way they were before exiting the interrupt and you can use any Basic statements you want.

I've probably said it too many times already but ... Thanks again Tim!
<hr>
ReEnterPBP.bas is an adaptation of the same concept, but it allows the Interrupt system to determine if it needs to save the variables or not.

For instance, if you have a program with both ASM and PBP interrupt handlers, and an interrupt triggers an ASM handler, there's no need to save the variables first, it would just be waisting valuable time. And if more than 1 Basic handler is triggered at the same time, it only saves the variables once, and processes all the Interrupts on the same pass, before restoring the system vars, again saving time.

However, it does still take a lot of time to save all those variables. Usually it takes around 70 instruction cycles to save the vars. Then another 70 cycles to restore them again. At 4mhz it's 140us total save and restore time, which limits the maximum interrupt frequency to just over 7khz. At 20mhz OSC, you can go up to almost 36khz. That's fast enough to receive RS232 at over 250Kbaud with the USART.   But is still considerably slower than you can get with ASM interrupts.

<br>

**Darrel Taylor** · - 19th March 2006, 20:33

</td><td>While working on the 18F version, I discovered a bug in the ReEnterPBP file.
It was not restoring the RS1 and RS2 system variables properly.</td></tr></table>The file has been updated to version 3.2, and anyone using Instant Interrupts for the 14-bit PIC's should update the file as soon as possible.

<br>

**Darrel Taylor** · - 11th July 2006, 10:20

</td><td>
At long last.

The Instant Interrupt system for 18F PIC's is now available.

It's become increasingly harder to keep things up to date here on the forum, so I've moved everything over to my website.
I'm still working on some of the pages, but everything you need is already there. It seems to take longer to make the web pages, than it does to write the program.

http://darreltaylor.com/DT_INTS-18/home.html</td></tr></table>

<br>

**Christopher4187** · - 12th July 2006, 03:03

Darrel,

Awesome program for a 18F4550. I never realized it takes so many lines of code just to blink an LED. Where can I adjust the duty cycle of the LED?

Thanks,

Chris

**Charles Linquis** · - 12th July 2006, 03:22

Many thanks to Darrel Taylor ! I'll have to try this immediately.

His techniques probably make most of what I'm about to write obsolete - but last night I promised that I would post what I learned about assembly-language interrupts and PBP from Tim Box, Charles Leo (of MELABS) and my own testing. The information presented is believed to be accurate, but I cannot guarantee this without complete testing - something I will do within the next few days. If I find any mistakes, I'll post an update.

1)
Some of the newer 18F parts have a new instruction -

RETFIE FAST

This instruction AUTOMATICALLY saves and restores the W,STATUS and BSR registers. Unless you mess around with pointers (such as FSR0x), this is all you need to do use. No extra instructions for saving and restoring context are needed. Just put it in place of the ordinary 'retfie' instruction. Check your datasheet to make sure if your part offers this. The 18F8720 and '8722 have this instruction.

2)
If your part does NOT have the "fast interrupt" enhancement, you should *normally* only need to save and restore W,STATUS and BSR.

3)
ALL of the variables declared by PBP but used in the assembly routine should be declared as 'bankA'.

4)
Variables declared by PBP are given an underscore "_" before the name when used in assembly. For example: 'MyVar var BYTE bankA' in PBP becomes '_MyVar' in assembly. To allow the same name in both PBP AND assembly, you need to define the variable as 'system' . For example 'MyVar BYTE bankA
system' has the name 'MyVar' in assembly (The assembler variable doesn't require an underscore as long as the variable is declared as 'system'.)

5)
Don't declare BIT variables in PBP to later be used in an assembly routine.
Use BYTE or WORD variables only. If you just need a bit to act as a flag, declare a PBP variable such as 'FLAGVAR' and set/reset one of the bits.

6)
Since your are only using the Access Bank (bankA) in your assembly-language routine, you don't need to use GOTOs. Use the BRA (branch) instruction instead.

7)
If you have two interrupt levels (high and low priority), you can use the PBP defines -
DEFINE INTHAND (label of high-priority interrupt handler) and
DEFINE INTLHAND (label of low-priority interrupt handler)

Save and restore context the same way as described above. RETFIE FAST works on the low-priority interrupt, too.

**SteveB** · - 12th July 2006, 03:42

Originally Posted by Charles Linquis

RETFIE FAST works on the low-priority interrupt, too.

Just to clarify one important item. Here is snippet from the PIC18F8722 Datasheet under Memory Organization:

5.1.4 FAST REGISTER STACK
...
If both low and high priority interrupts are enabled, the
stack registers cannot be used reliably to return from
low priority interrupts. If a high priority interrupt occurs
while servicing a low priority interrupt, the stack register
values stored by the low priority interrupt will be
overwritten. In these cases, users must save the key
registers in software during a low priority interrupt.

So, more accurately, RETFIE FAST works when low-priority interrupts are enabled, as long as software saves & restores key registers during the low priority interrupts, and RETFIE FAST is only used to return from high-priority interrupts.

Steve

**ozion** · - 28th October 2008, 23:50

Originally Posted by Darrel Taylor

</td><td>
At long last.

The Instant Interrupt system for 18F PIC's is now available.

It's become increasingly harder to keep things up to date here on the forum, so I've moved everything over to my website.
I'm still working on some of the pages, but everything you need is already there. It seems to take longer to make the web pages, than it does to write the program.

http://darreltaylor.com/DT_INTS-18/home.html</td></tr></table>

<br>

Thank you very much Darrel. Your excellent works have saved me lots of headache.

**savnik** · - 29th December 2006, 22:55

Originally Posted by Darrel Taylor

So far I've shown one interrupt source being used at a time, but as I said in the first post, you can easily service Multiple Interrupt Sources.   So what if we wanted to join the previous 3 examples into one program.   NOT a problem!

To add more interrupt "Handlers", simply add them to the INT_LIST, and create a subroutine for them.

Since both the Blinky Light, and Elapsed Timer used TMR1, lets move the Blinky Light over to TMR0. Elapsed will still use TMR1.

Code:

<font color="#000000"><b>LED1   </b><font color="#008000"><b>VAR  </b></font><b>PORTD</b>.<b>0
LED2   </b><font color="#008000"><b>VAR  </b></font><b>PORTD</b>.<b>1

</b><font color="#008000"><b>INCLUDE </b></font><font color="#FF0000">&quot;DT_INTS-14.bas&quot;     </font><font color="#0000FF"><b><i>' Base Interrupt System
</i></b></font><font color="#008000"><b>INCLUDE </b></font><font color="#FF0000">&quot;ReEnterPBP.bas&quot;     </font><font color="#0000FF"><b><i>' Include if using PBP interrupts
</i></b></font><font color="#008000"><b>INCLUDE </b></font><font color="#FF0000">&quot;Elapsed_INT.bas&quot;    </font><font color="#0000FF"><b><i>' Elapsed Timer Routines

</i></b></font><font color="#008000"><b>ASM
</b></font><font color="#000080">INT_LIST  macro    </font><font color="#0000FF"><b><i>; IntSource,        Label,  Type, ResetFlag?
        </i></b></font><font color="#000080">INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
        INT_Handler   TMR0_INT,  _ToggleLED2,   PBP,  yes
        INT_Handler   TMR1_INT,  _ClockCount,   PBP,  yes
    endm
    INT_CREATE               </font><font color="#0000FF"><b><i>; Creates the interrupt processor

    </i></b></font><font color="#000080">INT_ENABLE   INT_INT     </font><font color="#0000FF"><b><i>; enable external (INT) interrupts
    </i></b></font><font color="#000080">INT_ENABLE  TMR0_INT     </font><font color="#0000FF"><b><i>; enable Timer 0 interrupts
    </i></b></font><font color="#000080">INT_ENABLE  TMR1_INT     </font><font color="#0000FF"><b><i>; Enable Timer 1 Interrupts  
</i></b></font><font color="#008000"><b>ENDASM

</b></font><b>OPTION_REG </b>= <b>OPTION_REG </b>&amp; <b>$80 </b>| <b>1  </b><font color="#0000FF"><b><i>; Set TMR0 Prescaler to 256, leave RBPU alone
</i></b></font><font color="#008000"><b>GOSUB </b></font><b>ResetTime              </b><font color="#0000FF"><b><i>' Reset Time to  0d-00:00:00.00
</i></b></font><font color="#008000"><b>GOSUB </b></font><b>StartTimer             </b><font color="#0000FF"><b><i>' Start the Elapsed Timer

</i></b></font><b>Main</b>:
    <font color="#008000"><b>IF </b></font><b>SecondsChanged </b>= <b>1 </b><font color="#008000"><b>THEN  
       </b></font><b>SecondsChanged </b>= <b>0
       </b><font color="#008000"><b>LCDOUT </b></font><b>$FE</b>,<b>$C0</b>, <font color="#008000"><b>DEC </b></font><b>Days</b>,<font color="#FF0000">&quot;d-&quot;</font>,<font color="#008000"><b>DEC2 </b></font><b>Hours</b>,<font color="#FF0000">&quot;:&quot;</font>,<font color="#008000"><b>DEC2 </b></font><b>Minutes</b>,<font color="#FF0000">&quot;:&quot;</font>,<font color="#008000"><b>DEC2 </b></font><b>Seconds
    </b><font color="#008000"><b>ENDIF
GOTO </b></font><b>Main

</b><font color="#0000FF"><b><i>'---[INT - interrupt handler]---------------------------------------------------
</i></b></font><b>ToggleLED1</b>:
     <font color="#008000"><b>TOGGLE </b></font><b>LED1
</b><font color="#000080">@ INT_RETURN

</font><font color="#0000FF"><b><i>'---[TMR0 - interrupt handler]-------------------------------(Blinky Light)------
</i></b></font><b>T0Count  </b><font color="#008000"><b>VAR WORD
</b></font><b>ToggleLED2</b>:
    <b>T0Count </b>= <b>T0Count </b>+ <b>1
    </b><font color="#008000"><b>IF </b></font><b>T0Count </b>= <b>512 </b><font color="#008000"><b>THEN </b></font><b>T0Count </b>= <b>0 </b>: <font color="#008000"><b>TOGGLE </b></font><b>LED2
</b><font color="#000080">@ INT_RETURN
</font>

<font size=-2>Code Size = 711 Words</font>

Now we have all three interrupt sources working together in the same program.

LED1 responds to the external INT
LED2 flashes, timed by TMR0
and, the elapsed timer is maintained via TMR1

And, all of this is happening behind the scenes of your normal PBP program.

I test for 16f877a and it's work.
But for the 18f88 i got the message : Symbol not previously defined (T0IF)
and not compile.Why;

skimask · - 29th December 2006, 23:27

Originally Posted by savnik

I test for 16f877a and it's work.
But for the 18f88 i got the message : Symbol not previously defined (T0IF)
and not compile.Why;

That would be a good trick....compiling for an 18F88. I can't seem to find it on the Microchip website.

Try TMR0IF (a zero after TMR). Or you don't have an up-to-date version of PBP.

Previous Release: 2.45

* Adds support for PIC12F508, 509, 683, PIC16F505, 684, 688, 716, 737, 747, 767, 777, 87, 88, PIC18F2331, 2431, 2515, 2525, 2585, 2610, 2620, 2680, 4331, 4431, 4515, 4525, 4585, 4610, 4620, 4680, 6410, 6490, 8410 and 8490.

**savnik** · - 30th December 2006, 00:10

Originally Posted by skimask

Previous Release: 2.45

* Adds support for PIC12F508, 509, 683, PIC16F505, 684, 688, 716, 737, 747, 767, 777, 87, 88, PIC18F2331, 2431, 2515, 2525, 2585, 2610, 2620, 2680, 4331, 4431, 4515, 4525, 4585, 4610, 4620, 4680, 6410, 6490, 8410 and 8490.

I have 2.46

skimask · - 30th December 2006, 00:19

Originally Posted by savnik

I have 2.46

Well, if TMR0IF (or T0IF for that matter) doesn't work, then just change the code to access the interrupt flag bit directly from the applicable register.

**Darrel Taylor** · - 30th December 2006, 02:21

Microchip can't make up thier mind on what they want to call things. In most 16F's it's called T0IF, and in the 18F's it's TMR0IF, but for some reason, in a 16F88 it's also called TMR0IF. It's the same with the T0IE/TMR0IE.

Fortunately, we aren't stuck with whatever they decide to call things.

Just add the 2 highlighted lines, and you should be fine. (no spaces before them)

Code:

ASM
T0IF = TMR0IF
T0IE = TMR0IE
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
        INT_Handler   TMR0_INT,  _ToggleLED2,   PBP,  yes
        INT_Handler   TMR1_INT,  _ClockCount,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor

    INT_ENABLE   INT_INT     ; enable external (INT) interrupts
    INT_ENABLE  TMR0_INT     ; enable Timer 0 interrupts
    INT_ENABLE  TMR1_INT     ; Enable Timer 1 Interrupts  
ENDASM

**savnik** · - 30th December 2006, 09:48

Thank you.
Now it's work.

Thread: Instant Interrupts - Revisited

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