Anthony Toft wrote :

(First, we *are* talking about the Noritake CU20045SCPB-T23A, right ?)

> > Are you monitoring the BUSY line from the VFD ?
> 
> Yes, which is the most frustrating part, the datasheet says 
> to do it...
> I am using it in parallel mode,...

OK, my tests was done using the serial interface. I only
write "normal" characters to it and didn't use the BUSY line.

> here is the function as it appears in my
> code
> 
> #DEFINE WR PORTC,0
> #DEFINE CS PORTC,1
> #DEFINE BUSY PORTC,2
> 
>         ; Takes the contents of character and displays it.
> 
> DISPLAYCHAR        
>         ; wait for BUSY to be low...
> WAITBUSY
>         BTFSC BUSY
>         GOTO WAITBUSY
>         ; lower WR
>         BCF WR
>         
>         ; Load  data
>         MOVFW character
>         MOVWF PORTB
>         
>         ; raise wr
>         BSF WR
>         RETURN

Since you are running at (aprox) 20 Mhz, you have an Tcyc of 200 ns.
The mini setup time of the data lines before the rising edge of WR is
100 ns. It *should* be OK, but... There is also a slight delay
from the rising edge of WR until BUSY goes high. Just 200 ns "max"
according to the data sheet, so that should not be a problem. You
cold anyway try to put some NOP's to slow down the "clocking"
a little, just to be safe.

> 
> Notice I _don't_ use CS, but the datasheet is ambiguous about 
> it, could that be the problem?

I hope not :-)
I'm currently trying to get a similar unit (GU128X32-311) running,
and it also have a CS line that I was planning to set CS hard "low".

> 
> The POSCURSOR function calls this three times to output 0x1B, 'H' and
> the position. I have also tried this with various amounts of delay in
> here, using NOP anything from one to 255*255. This is on an 16F876A
> using a 19.8806Mhz crystal. The circuit can be seen at
> http://cowshed.8m.com/car/inputs.html

Is there anything connected to the "Programming" connector ?

>  When I was echoing the 
> serial RX
> to screen then it worked flawlessly (in Quick write, no 
> positioning) now
> I am working on startup, and probably driving the display pretty fast.
> The display is using flickerless mode at this time, but it happens
> regardless to the mode. I always seem to display 0x9D, the integration
> character, when it doesn't work quite right.

Is in *only* when sending the ESC-sequence for setting the position
that you get problems ? Or just about anythime ?

/Jan-Erik.

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