IF...THEN inside a Loop

[EarlyBird2]

Hi Bill

I do not think you are missing anything. The only thing I can see is that you should put parenthasis around you conditions when you use the AND statement but I can not see how that or why that would work with one chip and not another. I will read the data sheet on the PIC18F8722 but I am not hopeful. Generaly what I do in these cirumstances is to find a work round solution and then later on, some times years later, all becomes clear.

Steve

[Melanie]

What happens if X=1 ?

[sayzer]

What happens if X=1 ?

Also,
IF X<1 THEN PORTB=$F0 is the same as X = 0

IF X>1 AND X<3 THEN PORTB=$3C is the same as X = 2

IF X>2 THEN PORTB=$0F is the same as X = 3 ( For loop goes to 3)

Thus,

IF X = 0 THEN PORTB=$F0
IF X = 2 THEN PORTB=$3C
IF X = 3 THEN PORTB=$0F

looks better.

[Bill Legge]

Sorry - I made a silly mistake in the code I posted. The case where X=1 shows my error.

However, the real code that was/is causing trouble was for a larger range of X and included '>=', '<='.

My poor attempt to simplify the real problem failed!

I'll tidy up the real code and post it soonest.

Thanks for your input.

Regards Bill legge

[Bill Legge]

Sorry for my earlier muddled post. I've done some more work on the problem and have pinned down my difficulty.

I am compiling using PBPL and using a graphic LCD with 4 driver chips.
The GLCD is 240 pixels wide and I need to activate the Chip Selects as the display sweeps along:

0 to 63 CS1
64 to 127 CS2
128 to 191 CS3
192 to 239 CS4

The chip selects are connected to PORTB and my code is:

clear
DEFINE OSC 40	' Run on PIC18F8722, HSPPL
ADCON1	= $0F	' Set PortA to digital

TRISB=0               ' Make Port B outputs
PORTB=0	             ' clear the port

X	var	byte

Loop:
PORTB=$0		
for X = 0 to 239
	if X<64 then PORTB=$01
	if X>63 and X<128 then PORTB=$02
	if X>127 and X<192 then PORTB=$04
	if X>191 then PORTB=$08		
	pause 5
next X
goto Loop

If I compile using PBP it works properly and the chip selects turn on/off as X goes from 0 to 239.

If I compile using PBPL it does not work.

I need to use the LONG compilation. Any idea what is going wrong?

Regards Bill Legge

[Darrel Taylor]

Hi Bill,

No idea what's wrong at this point.
But I did run your program as is, no changes, on an 18F252.

Works the same with either PBPW or PBPL.

You can also do the same thing like this ...

for X = 0 to 239
  PORTB = DCD (X >> 6)
  pause 5
next X

Added:
So that it only affects those 4 pins, you could do this ...

PORTB = (PORTB & $F0) | DCD (X >> 6)

[mackrackit]

Silly question.
PM or MPASM ?
Or does it matter?

[kindows]

I am new with PICBASIC
I am trying to understand
Good luck for all.