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Hi All,

I have copied some code from the MOD5234 demo and tried to modify it for my memory configuration but I am not seeing the correct information on the logic analyser.

This is the code I used.

#define BASEADDRESS ( 0xA0000000 )

static volatile WORD *pDisplayCommand = ( WORD* ) (BASEADDRESS);
static volatile WORD *pDisplayData = ( WORD* ) (BASEADDRESS + 1);

My external device is on a 16 bit data bus. Here is the configuration I have used to setup the Chip select. I know this is working as I can see it on the logic analyser when I access that address but the databus is not correct. I have a feeling it is the above definition that is causing the issue. I can't find anything in the documentation on how to setup and use external memory other than the demo app I found.

sim.cs[2].csar = ( BASEADDRESS >> 16 );
sim.cs[2].cscr = 0x2180; // 0010 0001 1000 0000
sim.cs[2].csmr = 0x001F0001;

Cheers,
Dave...

I have a similar setup with an external 16-bit latch register I can read/write from.
The only weird thing I recall running into was that the 5282 puts 16-bit values out on address lines [16:32], bit 0 corresponds to address line 16, so if watching with a logic analyzer, it might look weird.


My chip select setup is identical to yours.

Here's a stripped down example of how I use it to write to an outlatch register sitting out at 0xd0000010.

volatile unsigned short * const outlatch = (unsigned short * const)0xd0000010;

To set it, I basically do this:
unsigned short foo=0x0001;
*outlatch = foo;

The only weird thing I see in your setup is:
static volatile WORD *pDisplayData = ( WORD* ) (BASEADDRESS + 1);

This puts the displayData at 0xa0000001, which isn't word aligned. Looks like you might want
static volatile WORD *pDisplayData = ( WORD* ) (BASEADDRESS + 2);
OR
static volatile WORD *pDisplayData = pDisplayCommand + 1;

Thanks Thomas,

My databus is indeed connected to DB16-31 as this is what is brought out to the IO pins. I used to work with the MC68332 many years ago so learned to know about the use of the bus. At that time it was all in assembly!!

I thought about using the word alignment. This is the confusing part. I currently have A1 connected to the IO device to act as the Command/Data selection (is an LCD interface) as I recall that A0 is not used due to the word alignment. I had forgotten about the pointer maths so thanks for pointing that out.

I'll test it later today.

Cheers,
Dave...

Got it.

If the address is not word aligned, the CPU outputs it as two 8 bit bytes instead.!!

Now just need the see if the LCD will respond now that the data is appearing on the bus.

Dave...

Just a quick update. I got it working tonight. I had to delay the A1 address and CS chip select to the LCD. There is an E enable input to the LCD that is a direct inverted version of the CS but I needed the small delay on A1 and CS so the E would fall before they changed state. A 74HC04 did the trick nicely as there was 5 spare gates on it anyway as this was used to generate E from CS in the design.

The LCD is now working in 16 bit mode on the MOD5234.

Cheers for all your comments.!

Dave...