Re: Mup21, features

[Andrew Sieber <asieber@xxxxxxxxxxx>]

>The other day I realised that the Video processor on the Mup21 is just a
>glorified D/A DMA machine, so if you can modulate a picture out on a
>specific frequency, why not the sound channel as well.  Well I looked up my
>copy of the Mc grawlls Television handbook and of course the sound channel
>is modulated at a different frequency (that is too far away from the TV
>frequency), but I did notice that picture elments can effect the sound
>channel.
Somebody please correct me if I'm wrong, but I believe that a standard
composite video signal carries no sound information.  For broadcasting,
the composite signal is amplitude-modulated on a 60-or-so megahertz
carrier (carrier frequency being of course dependent on which channel
you are using.)  Then the audio information is frequency-modulated and
sent along with the separate video signal, and a TV is really a TV and
FM radio combined into one, because it decodes two separate signals: the
AM video signal and the FM audio signal.  The MuP21 can produce a
composite
video signal, but you can't put sound on this signal.  You could,
however,
use another P21 with an extremely slow "video" clock (like 22kHz) and
put
digitized sound information where the "video" signal for the DMA D/A
converter is supposed to be.  This P21 would then produce an audio
signal
that you could actually amplify and hook to a speaker and directly
listen
to.  You could hook the video signal to a TV and the audio signal
to your stereo system.  Or you could AM modulate the video signal and
FM modulate the audio signal, and send both of these signals to the
antenna jack on your TV and it would display the video and emit the
audio.

>I came accross something interesting in a jornal the other day, it was
>called NVSRAM I think, by a company called Simtek, I think they used to
>produce 6502 chips.  The company claimed that they were non-volatile,
>operated at 25ns, something I can't rember but it led led me to beleive they
>were not flash and did not have limited write cycles, and available is sizes
>upto 256KB.  Well this was very interesting, a chip that could replace
>bother rom and ram in a design?  If the 256KB was available in 32-bit
>version (some srams are) then one NVSRAM and MUP21= 1 computer
>(simplictically speaking).  If in 8-bit versions, 3*8-bit NVSRAM= 256kwords
>of memory.
Are you talking about battery-backed sram?  There are sram chips made
that actually have a battery inside the plastic package for the chip,
and automatically battery-back the sram when power to the chip is
removed.
These batteries can often last for a decade, so what you get is
effectively
a super-high-speed-write eeprom with unlimited write cycles.  You don't
have to deal with an external battery or support circuitry because it is
all integrated right into the chip's package.  Jameco sells a 256kB
version
for $27.95 (according to my late-1996 catalog.)  Dallas Semiconductor
makes
the chip that Jameco sells.


I've got two questions about the MuP21 myself.
1: The S21 simulator program will execute a jmp-if-T=0 if the T register
contains a 000000 OR a 100000.  It appears to be ignoring the carry bit!
Is this a fluke in the simulator, or is this actually how P21 operates?
2: The T=0 instruction says that if you have an instruction before a
jump-if-T=0 instruction in the same word, that first instruction may not
change the T register.  If it does, the condition for the T=0 will
depend
on the state of T BEFORE that first instruction is executed.  Well this
seems rather useful: since the IF instruction in Forth consumes the
flag, while jump-if-T=0 does not, you could have a word that does this:
drop jmp-if-T=0 aaaaa aaaaa
where the a's are the address to jump to.  This would result in a
jmp-if-T=0
instruction that DOES consume the flag.  The same would be the case for
the jmp-if-carry=0.  Will this trick actually work?

--Andrew Sieber
asieber@hotmail.com