Div32

Hello Everyone,
Still in an effort to understand this programming language, I now am playing with DIV32.
I have taken the code from the manual and added some serial routines so I can view whats happening. I have posted the code below.

Code:

---

' Use MPASM
@MyConfig = _HS_OSC & _WDT_OFF & _PWRTE_ON & _MCLRE_ON & _LVP_OFF
@MyConfig = MyConfig  & _CP_OFF & _BODEN_OFF & _DATA_CP_OFF
@ __config  MyConfig
Define PIC16F628A
define OSC 20
include "modedefs.bas"


a    var word
b    var word
c    var word
Dummy var word
start:
 b = 500
 c = 1000
 
 disable '
 
 dummy = b * c
 a = div32 100

 enable
 serout PortB.4,T9600,[254,1]
 pause 100
 serout PortB.4,T9600,[254,128,"dummy is:",# Dummy]
 pause 1000
 serout PortB.4,T9600,[254,192,"A is:", # a]
 pause 1000
 serout PortB.4,T9600,[254,148,"B is:", # b]
 pause 1000
 serout PortB.4,T9600,[254,212,"C is:", # c]
 pause 1000
 goto start
end

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The code does what the book says it should do. I have a couple of questions:
the line, a = DIV32 100 . I get that the 100 causes DIV32 to divide by 100, what I do not get is how DIV32 knows to use the math in the above formula, is "Dummy " a default place holder? My second question is the value of Dummy as outputted in line 1 of the display, I get the fact, 5 hundred thousand is too large for 16 bits to hold but 41248 makes no sense to me, can anyone explain?
Thank You
JS

Windows Calc commes pretty handy in this case... 500,000=07 A1 20 hex right?

As Dummy is a WORD, it keep only A1 20, witch equate to 41248.

you could still use

Code:

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A = b * c
 a = div32 100

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or

Code:

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B = b * c
 B = div32 100

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Quote:

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Originally Posted by mister_e

Windows Calc commes pretty handy in this case... 500,000=07 A1 20 hex right?

---

Thank You Mister_e, that leads me into another question:
I thought microprocessors worked only in binary, logic high and logic low, so why do we use hex anyway? Is it because we have 16 bits?

Why decimal, why Hex, why Octal and why Binary... it's just different measure like Km/h Mph, Mils or mm, Yard Meter.

In the previous, it's easier to figure out the problem with Hex than Decimal. A word is indeed 16 bits (uh...). PBP don't have any LongWord or DoubleWord var, DIV32 work around that.

Bad explanation i know... It's clear in my little head, but right words won't go out :D

Hey Joe,
Have a look at Darrel's Threads using DIV32 and other 32 bit math magic. Good stuff from the Wizard.
Retrieving 32bit Multiply Result
Retrieving Div32 Remainder
32-bit Variables and DIV32, Hourmeter 99999.9


SteveB

Thanks.
Iwill look at those threads too.
Joe

Edit:Those are great, I have bookmarked these pages and stashed the code samples for study.