| Author |
Message |
Dimitris Stafylarakis
Guest
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 Posted:
Sat Jan 08, 2005 3:58 am Post subject:
Philips P89c669 question |
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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 |
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Jim Granville
Guest
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| Posted:
Sat Jan 08, 2005 5:48 am Post subject:
Re: Philips P89c669 question |
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Dimitris Stafylarakis wrote:
| Quote: | 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 |
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Dimitris Stafylarakis
Guest
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| Posted:
Sat Jan 08, 2005 6:21 am Post subject:
Re: Philips P89c669 question |
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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
##Remove .no.spam from e-mail address##
"Jim Granville" <no.spam@designtools.co.nz> wrote in message
news:41df2db6@clear.net.nz...
| Quote: | 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
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