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Misim DE Pic simulator

Thread starter #1
Hi, does anyone know where to obtain the MiSim DE 2.1 Pic simulator by Feersum? I believe it was made freeware before being abandoned. As a newcomer to PICs I find MPLAB somewhat overwhelming.


Well-Known Member

Cannot help with that MiSim, perhaps others now of it ?

When you say Mplab is overwhelming do you mean MplabX ?

Mplab v 8.92 was the last release of the old IDE and much simpler to use, some on the forum still prefer it to MplabX.

You need to mention which compiler and chip family you are using and if you are looking for full software simulation ?

You can get v8.92 if you log in to Microchip, who also have a good forum.

or direct from this site which also gives a good overview of v8.92
Thread starter #3
Thanks, I found an old printout of a web page amongst my general bric-a-brac, while having a clearout, and found a program for using a small pic to drive a stepper motor with a ULN2803.

I thought it would be an interesting small project to begin learning about PICs.
I worked in Avionics all my life before retirement, and have no fears about electronics, but have slight knowledge of coding.
I thought I could port the program to a 12F509, and managed to get MPLAB 8.92 to compile the program as a 12F509, with some warnings.(which I do not understand)

I want to breadboard it (I have a Pickit3) but before that, I had thought to simulate the program using LEDs to monitor the motor drive outputs from the PIC, and have tried the demo of Real Pic Simulator, but although it has the 12F509 in it when I tried to run it I got an error message "Error out of code". An email to Digital Electo Soft evinced no reply, and as I don't know if it is a limitation of the demo version or something else, I am reluctant to spend any dosh yet.
I cannot understand the MPLAB simulator (especially the MPLABX version, I find MPLAB X very difficult to understand).
I have all the Oshonsoft compilers and simulators, but here is no 12C/F50x pic support.
I had hoped the Misim DE, being older might support them, but it seems unobtainable.
The Proteus simulator does support them, but is very expensive for the hobbyist.

Is it very difficult to port to a supported 8 pin PIC, say a 12F629? though they seem much more complicated.

here is the code from the (no longer available) website.

I also don't understand what



mean, are they registers? or variables?

;    control a small stepper motor with a 12C509

;    There are two controls, run/stop and direction
;    The motor steps when the run button is depressed
;    If the direction button is pressed
;    the direction is reversed

;    Peter Lynch, 13 May 1998
;    pic@beowulf.demon.co.uk    (THIS SITE NO LONGER EXISTS newpicuser)

;    (this code is NOT certified Year 2000 compliant)

        LIST P=12C509        ; (deleted by newpicuser)

        include "\picde\12c509.inc"    ; (changed to #include <p12c508.inc> newpicuser)

OPMASK    EQU    B'11000000'
BMASK    EQU    B'00101000'    ; all bits output (except GP3 and GP5)
                ; GP3 controls run/stop
                ; GP5 controls direction

RUN_BTN    EQU    3
DIR_BTN    EQU    5

DELAY1    EQU    0C
DELAY2    EQU    0D

INDEX    EQU    0E        ; step index

    ORG 0

; start of main code


    TRIS    GPIO

; now go into a loop, output the next bit pattern on
; GP0 - GP4 (GP3 is input only)



; check for run/stop button

    GOTO    NEXT


    INCF    INDEX, W

    DECF    INDEX, W
    ANDLW    .7

; here W contains the index (either incremented or decremented, depending
; on the direction switch) into the array for the new stepper actuations

    CALL    STEP        ; convert the index into a bit pattern


; routine to get step index

    ADDWF    PCL, F
    RETLW    B'00000001'
    RETLW    B'00000101'
    RETLW    B'00000100'
    RETLW    B'00000110'
    RETLW    B'00000010'
    RETLW    B'00010010'
    RETLW    B'00010000'
    RETLW    B'00010001'

; routine to delay between steps


    MOVLW    .10        ; 10 milliseconds per step

    MOVLW    .250        ; 1 millisecond delay


    GOTO    DEL_1

    GOTO    DEL_0

    RETURN    ; (changed by MPLAB to RETLW 0 newpicuser)


I will have to reinstall MPLAB 8.92 as it now longer runs since MPLAB-X updated itself to 5.10
Sorry for the long post, any help/comments will be appreciated.
Delay1 and 2 are simply a "count" to loop for to create a specific delay time in software. This would be based on the chip frequency. Since I don't see any frequency specification, I would assume the PIC is running at the default 4Mhz.
Index is a pointer into the "Step:" routine, to get a specific bit pattern for output.. It's like a program counter offset.
Thread starter #5
Just noticed a typo in my last post.
Should be #include <p12c509.inc>
So the 0C,0D are hex starting values?
And Index 0E is an address in a register?


Well-Known Member
Just noticed a typo in my last post.
Should be #include <p12c509.inc>
So the 0C,0D are hex starting values?
And Index 0E is an address in a register?

Yes, just found that when I built your code, though the 12C chip is the one time programmable chip, you need to change the LIST and Include lines to 12F, which will build ok and then allow you to your your Pickit programmer.

You also need to Configure, Select Device and change the 12C to 12F

If you View, File Registers , you will see what those variable are.

Quiet a few of us in the forum started with Assembly code and one member , Nigel, has written a good tutorial you might find interesting, he is still around to help.
If you see the Sticky above there are links to a lot more pic info which will help you get going.

Afraid I have only used the most basic functions of mplab sim, perhaps other can help, though as you will see on the web etc a lot of folk use Proteus for simulations , though as will all of them there are limitations and bugs.
Personally still prefer to build and test my own hardware, for motors I made up a board with a couple of different types of motrs .stepper, servo, all just a few pound from a local hobby shop or online.



Well-Known Member

Just looked back about 8-9 years ago to find the motor board and assembly code I used, driven by the L298 motor chip which you can buy as a complete driver module for just a few pounds on the usual uk sites

Though using a larger chip, the 18F, it does contain some extra routines you might find of use in the future.


Just noticed a typo in my last post.
Should be #include <p12c509.inc>
So the 0C,0D are hex starting values?
And Index 0E is an address in a register?
Index is added to the program counter in the "Step:" routine, to basically create a jump offset to the PCL. Index is a value that is incremented or decremented based on previous value. The returned value from the "Step" routine give the different pin outputs to step the motor.

The 12F509 is an older chip. Look into the 12F675, it is the same pinouts and is more common/easier to find. The Oshonsoft compiler will handle it just fine. You can find 12F675 real cheap on places like Ebay. The 12F683 is one step higher than the 675, and again, cheap to find. Both of those series have more features as well.
I'd strongly recommend not starting with the 8 pin PIC series as they cannot be used with in-circuit debugging.
You have a Pickit 3 which I believe does support in-circuit debug on devices that have that facility.

I find that invaluable - being able to step through a program running on "live" hardware makes things infinitely easier than working blind when trying to find a bug.

It also allows you to see what is happening with the CPU registers step-by-step and helps understand how the CPU is executing your program.

(There was at one time a special PIC12 IDC device, a 14 pin MCU with eight pins matching the standard PIC12 layout and extras to support simultaneous debug connections - but I cannot find any reference to those now, it looks like they are no longer made..)

Ian Rogers

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Thread starter #12
This is probably a dumb question, but what does the B in the line

EQU B'11000000'

Is it to denote a binary number, or is it a bank/register?
Google has not helped to answer this.

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