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From: anthony fremont on 12 Mar 2010 22:03
On Mar 12, 10:50 am, Jan Panteltje <pNaonStpealm...(a)yahoo.com> wrote:

You should be using a shadow register.
From: Spehro Pefhany on 12 Mar 2010 23:14
On Thu, 11 Mar 2010 22:40:54 GMT, the renowned Jan Panteltje
<pNaonStpealmtje(a)yahoo.com> wrote:

>I was writing a driver for a graphics LCD for PIC 18F14K22.
>That went OK:
> ftp://panteltje.com/pub/graphics_lcd_driver_img_1_1861.jpg
>
>But I wrote it is asm, so it needed a lot of typing,
>even more so because this display CD-19-HG1286418C has a strange
>driver chip S6B0108 that comes from a planet where x is vertical and y horizontal,
>and people write from to top to bottom probably on the right side towards the left...
>and the display uses 2 driver chips for each half... so it took a lot of key hitting:
> ftp://panteltje.com/pub/key_soup_img_1853.jpg
>to get it to do things the European way, that I then reversed with x0, y0 at bottom left as
>that is easier for what I want to do.
>
>But now about the problem.
>I did all this with the 8 MHz PIC internal clock, and it works perfectly.
>Activated the internal 4 x PLL, so to 64 MHz internal clock, results in 16MHz processor clock.
>
>Display stopped working, only display on and display off command still worked,.
>Well, added the usual delay between I/O operations, but this time,
>even with seconds delay, no effect.
>Finally grabbed the scope, and looked at the PIC pins.
>Now this is strange:
>
> bsf PORTA,1 ; pin 18 LCD_C_D
> bcf PORTA,5 ; pin 2 LCD_WR

Umm... why in the world would you do a Read-Modify-Write instruction
on a PIC PORT when you are trying to toggle at high speed?

Change PORTA to LATA and see what happens.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff(a)interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
From: Martin Riddle on 12 Mar 2010 23:50


"Jan Panteltje" <pNaonStpealmtje(a)yahoo.com> wrote in message
news:hnbri1$pu0$1(a)news.albasani.net...
> I was writing a driver for a graphics LCD for PIC 18F14K22.
> That went OK:
> ftp://panteltje.com/pub/graphics_lcd_driver_img_1_1861.jpg
>
> But I wrote it is asm, so it needed a lot of typing,
> even more so because this display CD-19-HG1286418C has a strange
> driver chip S6B0108 that comes from a planet where x is vertical and y
> horizontal,
> and people write from to top to bottom probably on the right side
> towards the left...
> and the display uses 2 driver chips for each half... so it took a lot
> of key hitting:
> ftp://panteltje.com/pub/key_soup_img_1853.jpg
> to get it to do things the European way, that I then reversed with x0,
> y0 at bottom left as
> that is easier for what I want to do.
>
> But now about the problem.
> I did all this with the 8 MHz PIC internal clock, and it works
> perfectly.
> Activated the internal 4 x PLL, so to 64 MHz internal clock, results
> in 16MHz processor clock.
>
> Display stopped working, only display on and display off command still
> worked,.
> Well, added the usual delay between I/O operations, but this time,
> even with seconds delay, no effect.
> Finally grabbed the scope, and looked at the PIC pins.
> Now this is strange:
>
> bsf PORTA,1 ; pin 18 LCD_C_D
> bcf PORTA,5 ; pin 2 LCD_WR
>
> should set pin 18, and then clear pin 2
>
> This is what happens at 16 MHz clock.
> But at 64 MHz clock after the first instruction pin 18 does not go
> high,
>
>
>
> ||||||||||||||||||||||||||||||||||||||
> porta, 1
> _________||||||||||||||||||||||||||||||||||||||_____________________
> pin 18
> 16 MHz RF
>
> -----------------------------------------------
> |
> porta, 5
>
> |_________________________ pin 2
>
> ^ ^
> | |
> bsf PORTA,1 bcf PORTA,5
>
>
>
> but start outputting 16 MHz until the second instruction, and then
> goes to _zero_,
> the second instruction operates normally and clears pin 2.
>
>
> It seems the PIC internal output FF for pin 18 does not toggle, but
> just follows the internal clock.
>
> I suspected a load problem and added an emitter follower because it
> drives a 20 cm long flat cable to the LCD.
> pin 18 is also the PGC (program clock) for in circuit programming, but
> the effect persists with
> pin 18 loaded with with only about 1k to ground.
>
> I think the PIC is out of spec here, but not sure if I am allowed to
> use it with 64 MHz on internal oscillator.
> Went back to 16 MHz clock, will work with that for now,
> will have to get some more PICs too to see if it is only this one....
> FYI.
>
>
>
>

What voltage are you running at?
VCO range is 20mhz at 1.8 to 3.0v, and 64mhz for 3.0 to 5.0v


Cheers



From: Jan Panteltje on 13 Mar 2010 08:15
On a sunny day (Fri, 12 Mar 2010 23:50:01 -0500) it happened "Martin Riddle"
<martin_rid(a)verizon.net> wrote in <hnf5i0$qac$1(a)news.eternal-september.org>:
What voltage are you running at?
>VCO range is 20mhz at 1.8 to 3.0v, and 64mhz for 3.0 to 5.0v

5.18V
From: Paul E. Schoen on 13 Mar 2010 20:19

"Paul E. Schoen" <paul(a)pstech-inc.com> wrote in message
news:CGWmn.72788$1n5.50230(a)newsfe04.iad...
>
>
> It seems reasonable that a BSF instruction might have a problem for an IO
> pin, compared to a standard memory register, because it must (in one
> cycle) read, modify, and write the modified byte to the port. This will
> certainly take longer than an internal file register. I am surprised that
> the code does not automatically use the LAT register, but there may be
> compatibility issues. The 12F and 16F chips do not have the LAT registers,
> but they also probably do not have a 64MHz option.

Interesting trivia: From the datasheet in PORTA:

"Reading the PORTA register reads the status of the
pins, whereas writing to it, will write to the PORT latch."

It does not say this about the B or C ports. But you are using Port A, as I
recall...

Hmmmmm

Paul

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