IF...THEN inside a Loop

[Bill Legge]

The following code executes correctly on a PIC16F877A at 20 MHz but not on a PIC18F8722 at 10 or 40 MHz:

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

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

X var byte

Loop:
PORTB=$0		
FOR X = 0 to 3
	IF X<1 THEN PORTB=$F0
	IF X>1 AND X<3 THEN PORTB=$3C
	IF X>2 THEN PORTB=$0F		
	PAUSE 1000
NEXT X
GOTO Loop

Please note:
1. With two IF...THENs inside the loop - all is OK.
2. I know that it would be easier to use
IF X=1 THEN....
IF X=2 THEN...
Etc, but this is a simplification of my real code.
3. I've tried a lot of variations but anything with multiple (>2) IF....THENs inside the loop will not work.
4. LEDs on PORTB work OK with
FOR X=0 TO 255
PORTB=X
NEXT X
5. Going nuts on this. What am I missing?

Regards Bill Legge

[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

[kindows]

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