From: Wolfgang Moser (womo_at_news.trikaliotis.net)
Date: 2006-10-08 21:34:02
Heya Spiro,
Spiro Trikaliotis schrieb:
> "André Fachat" wrote:
>> Considering CPU+USB combinations - I found a place with 6502 with
>> builtin USB: http://www.jesstech.com/new/english/jes.HTML_Product.phtml?id=5#
>
> 256 Byte (!) of RAM does not seem very much to me, especially for
> transfer solutions. Of course, it depends on whether you can add some
That amount of RAM (mostly 128 Byte) is pretty normal for
µCs, regardless if using PICs, ATmels, 8051 or else.
> external memory, too. According to the data sheets, this is not possible
> (directly), although you could add RAM via the general purpose I/O
With most µCs I looked at, you wouldn't want to add
external RAM. Exactly because you would lose many I/Os.
> lines. Anyway, in this case, this is no one-chip solution anymore. ;)
And here again my beloved EZ-USBs jump in, because with
their architecture design, there is already 16kB of on-chip
"external" RAM without losing any I/O pin. On Cypress' 8051
implementation, derived from Dallas' 8051 implementation
with extensions, that external RAM is not only connected to
program memory space (8051 in general is a Harvard
architecture design!), but to data memory also (through
autopointers, one of the twisted aspects). This gives the
ability to implement at least some buffers within that RAM
is not needed for code.
Btw. 8051 also does only contain 128 Byte of RAM (!)
Beside all the tweaks and especially the exclusive side
effects, the EZ-USB 8051 implementation allows to discover
more and more tricks for _years_, when your programming
experience grows. It remembers me to discovering and
making use of all the "bugs" (side effects) of the VIC-II
chip ;-) But well, we already had a deep talk about 8051.
For the rest of this list, please note that I am in no way
an expert in 8051 in general or EZ-USB in special. Just
some sort of beginner feeling happy with that weird thing.
Womo
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