Hi, I was wondering what size of internal RAM does P89C668 have? all 8051 processors have 128 bytes plus 128 bytes of SFR. I have read that some 8051 microcontrollers have an additional memory block of 128 locations to be use in parallel to SFR. this additional memory is accessed using indirect register addressing. how can i know if this additional memory does exist in a micrcontroller as micrcontroller datasheets seem hard to get? can i rely on the assembler IDE and use "indirect addressing" on any address between 80 and FF? if the assembler accepts my instruction this means that the micrcontroller has this embedded memory. Cheers
"as micrcontroller datasheets seem hard to get?"
Simple: if you can't find the datasheet for some particular chip (microcontroller or otherwise), just don't use it!
The Datasheet is the prime reference; it is absolutely essential to any & all use of the chip. So, if you can't find the datasheet, the chip is essentially useless. Avoid it.
However, the datasheet for the P89C668 is easily found: it's an NXP part so, obviously, go to the NXP website:
[the NXP URL seems to be what's causing the problem?]
It is also supported by Keil - so try Keil's search:
www.keil.com/.../search.asp
"can i rely on the assembler IDE and use "indirect addressing" on any address between 80 and FF?"
Again, Please read the manual - the Assembler Manual will describe this.
"if the assembler accepts my instruction this means that the micrcontroller has this embedded memory."
Not at all!
The forum kept giving HTTP 500.100 errors until I removed the NXP URL!
So you'll just have to go to the NXP site yourself, and put "P89C668" into the 'Search' box there...
(not really that hard, though, is it?)
I copied & pasted the URL, but it seems that there was a nasty invisible character hidden in it somewhere!
The URL should be:
www.nxp.com/.../P89c668hba.html
Thanks Neil. I got the datasheet and all the request information is in it. acutally the P89 has 8k internal RAM
cheers
Wasn't that hard, was it?!
"all the request information is in it."
Of course it is - that's the whole point of a datasheet!
"acutally the P89 (sic) has 8k internal RAM"
Note that "the P89" is meaningless - it's just a prefix shared by lots of NXP's 8051 derivatives! It's the '668 part that's significant - but better to get into the habit of always giving the full part number.
And you do understand that this "8K internal RAM" includes both IDATA and XDATA - don't you?