Hi Erik,

> I am a very strong proponent of using ICE as a hardware and software debugging tool,
> I get by very well with the Ceibo EB-51 which is 98% as good as the expensive ones at 1/4 the cost.
I've always used them in the past - many years ago (10?) I used the Ashling one for 8051 and since then many others including BDM/COP ones for Motorola devices - my processor make of choice ;-)
I will look into the merits of the EB-51 - thanks. Actually I've just discovered that Ceibo have been bought(?) by Kanda and the EB-51 was the one I was looking at anyway - thanks for the guidance!

I am writing the software for 5 different cards - virtually same digital architecture - so I've written a generic bootcode that will allow external FLASH programming and/or jump to the application stored in external Flash.

> You are aware of the function of the !EA pin, I hope
From what I can see - I need /EA low to run from internal flash or high if I need to run from external.
I believe if I keep EA high I will get memory-space 0000H-1FFFH internal and 2000H- external ?

>> "/PSEN, /RD connected to /OE of FLASH
>> This allows instruction fetching and 'const code' data read."
> You do not need this, and it may even get you in trouble, Compilers automatically use MOVC for "const"
I hadn't realised that a 'const' would get moved as if it's a code-byte - so I just need PSEN then ?

>> "Y2 from decoder connected to /CE of FLASH
>> This bit is set by writing to an address with A15 - hence writes to H8000+ will write into FLASH."
> I believe that is 0x8000- 0xBfff, please verify.
Yes, sorry.

> Also, this disables the access you want for 0x0000-0x3fff.
Oh dear - I thought this was the area I would have problems... conflicts between RAM and FLASH...

I must admit I'm getting a little confused :-)

So...
PSEN allows me to access EXTFLASH as program store/'constant code' data.

A0-A15 are used to select/access FLASH - A14/A15 decoded - this gives addresses 8000-9FFF for FLASH_WRITE
To FLASH_READ I only have A0-A13 (8K range) connected to it.. ie 0000-1FFF
Since RAM is addressed in the range 0000-1FFF then that is my conflict?

Could I possibly use another Yn output from my decoder to move the FLASH_READ area in memory? I haven't any outputs left but I may find a way?

If not - do you think there is a solution to this? (I'm amazed there seem to be no example schematics available anywhere utilising FLASH and RAM - maybe I'm looking in the wrong places).

Lots of Fun!

Kev