Olin Lathrop wrote:
>
> > status  equ     0x07            ; status register
> > rp0     equ     5               ;
> > carry   equ     0               ; the carry bit
> >
> >         ;; port B configuration
> > portb   equ     0x06            ; I/O port B
> > serio   equ     7               ; the serial i/o is RB7
> > sda     equ     5               ; SDA is RB5
> > scl     equ     4               ; SCL is RB4
> >
> > trisb   equ     0x86            ; trisb is the direction register for port
> B
>
> DON'T DO THIS!!!!  (This must be about the 20th time this has come up in the
> last year).

Horses for courses. Beginners may not know about or understand "include"
files yet. I certainly wrote code this way when I first started with
MPALC.


I missed the STATUS definition when I wrote back last time. It should be
defined as...

status  equ 0x03


Also your config value is not valid because the Code Protect bits are
trying to be set in opposite values.

        __config        0x1ff9

It should be...

        __config        0x3ff9

Now, if you decide to use an "include" file for this project this is how
your program start could look like....


        ;; program to send 'A' on the serial port
        ;;
        list    f=INHX8M, p=16F84

        #include "p16f84.inc"

        __config _CP_OFF & _PWRTE_OFF & _WDT_OFF & _XT_OSC

;
; PORTB BIT DEFINITIONS
;
serio   equ     7               ; the serial i/o is RB7
sda     equ     5               ; SDA is RB5
scl     equ     4               ; SCL is RB4
;
; RAM DEFINITIONS
;
        CBLOCK 0x0C

sobuf   ; serial output buffer
sibuf   ; serial input buffer
sctr    ; counter for bits to output to serial port
delay   ; wait counter for serial i/o

        ENDC

        ;; beginning of the program
        ;; jump over the interrupt vector
        org     0

init    goto    start


If you look inside the MPLAB directory you will see a whole list of
*.inc files. If you open 'p16f84.inc' using 'Notepad', you will see that
all the internal registers and thier bits are defined for you. Because
you included this file with your source code, MPASM will assemble this
file and your source code and thus have all the register data it needs.
This means you don't have to specifically define each one yourself.

One thing to take note of with this approach is that inside the include
files, the registers are defined in UPPERCASE so you either have to type
the register names etc. in upper case, or turn off the "case
sensitivity" option. Failing to do this will result in errors produced.
Try both ways to see what happens.

eg.  status,rp0 should be STATUS,RP0 with case sensitivity active.

You will probably need to have a look at these files if you use them so
that you make sure your register definitions are the same as the ones
written.

eg. you might define the OPTION register as "OPTION" in your code and it
is defined as "OPTION_REG" in the include file. This will create an
error. Try it and see.

The CONFIG information is also written in this file and makes it easier
for you to set the FUSE bits. Looking above, you can see how much easier
it is to understand now.


Also, I used a CBLOCK statement which sets an address for your RAM
definitions. You can see that it starts at address 0x0C which is the
start of the RAM address space in the 16F84.

eg CBLOCK 0x0C.

Just enter your RAM names in between the CBLOCK and ENDC statements and
MPASM will automatically assign incremental addresses for each one.

To verify this, have a look at the list file (*.lst) produced after
assembly and you will see the address data listed next to each
definition.

Have a look at the MPASM help file and look up CBLOCK for more info.

--
Best regards

Tony

mICros
http://www.bubblesoftonline.com
mailto:sales@bubblesoftonline.com

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