Philips P89c669 question

Hello,
I am about to use a P89c669 in a design with external program memory. 
Problem is that the manual states that EA pin either disables external 
program memory when held HIGH, or disables internal flash when EA is held 
LOW. The feedback I got from Philips is that when EA is held HIGH (???) both 
external and internal memory can be used in a mixed mode. So the big 
question is, if I want to use both program memories, how do I do it? I would 
appreciate any help on it.

Thanks beforehand
Dimitris

Dimitris Stafylarakis wrote:
> Hello,
> I am about to use a P89c669 in a design with external program memory. 
> Problem is that the manual states that EA pin either disables external 
> program memory when held HIGH, or disables internal flash when EA is held 
> LOW. The feedback I got from Philips is that when EA is held HIGH (???) both 
> external and internal memory can be used in a mixed mode. So the big 
> question is, if I want to use both program memories, how do I do it? I would 
> appreciate any help on it.

"normal" operation for 89C5x is for EA LOW to turn the device into
full 64K = External ROM [Romless], and when EA is HI, for On Chip FLASH 
memory to be used, where available.
  Above that limit, execution moves to external/off chip memory, but is 
dependant on lock bits.
[you normally can disable off chip execution if you want - see
the section on security bits for more details on Int.Ext code]

-jg

quote from the manual:
"EA must be externally held LOW to enable the device to fetch code from 
external program memory locations. If EA is held HIGH, the device executes 
from internal program memory"

I think you'll agree that what you suggest isn't exactly cried out by this 
sentence, right? But then again, no datasheet is ever clear..Anyway, thanks 
for the advice, I'll give it a try.

-- 
Dimitris Stafylarakis

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"Jim Granville" <no.spam@designtools.co.nz> wrote in message 
news:41df2db6@clear.net.nz...
> Dimitris Stafylarakis wrote:
>> Hello,
>> I am about to use a P89c669 in a design with external program memory. 
>> Problem is that the manual states that EA pin either disables external 
>> program memory when held HIGH, or disables internal flash when EA is held 
>> LOW. The feedback I got from Philips is that when EA is held HIGH (???) 
>> both external and internal memory can be used in a mixed mode. So the big 
>> question is, if I want to use both program memories, how do I do it? I 
>> would appreciate any help on it.
>
> "normal" operation for 89C5x is for EA LOW to turn the device into
> full 64K = External ROM [Romless], and when EA is HI, for On Chip FLASH 
> memory to be used, where available.
>  Above that limit, execution moves to external/off chip memory, but is 
> dependant on lock bits.
> [you normally can disable off chip execution if you want - see
> the section on security bits for more details on Int.Ext code]
>
> -jg
>