4 Questions about 68K based design.
Andy Warner
I have 4 questions about a 68xxx based design I'm about to
embark upon:-
1. Is there any problem running a 16MHz CPU with an 8MHZ
68450 DMA controller ? Does the async nature of the 68k
bus cope with this ? I can only see the problem being
major when the CPU was addressing the DMA.
2. Is there a better/cheaper 4 channel DMA chip than the 450 ?
3. I hear rumours of PLA equations for interfacing a Zilog
SCC (8530) to a 68k bus, does anyone have these ?
4. With the 68330, if an external bus master accesses memory
selected by one of the on-chip CS* lines, does the CS*
work ? Do DSACKn* or wait states get asserted ?
Any help/advice will be appreciated.
--
andyw. (W0/G1XRL)
an...@aspen.cray.com Andy Warner, Cray Research, Inc. (612) 683-5835
Bruce M. Walker
> 2. Is there a better/cheaper 4 channel DMA chip than the 450 ?
they may not run fast enough for you, I don't think Zilog has kept up
with rising CPU clock rates with this part).
> 3. I hear rumours of PLA equations for interfacing a Zilog
> SCC (8530) to a 68k bus, does anyone have these ?
Check out the 1991 Zilog Datacomm IC's databook. Pages 621 and 697
contain two app notes on this. 697 describes a 20X10 PAL to intfc
any Z85xx part to a 68K. Take a look at the ISCC and page 621 which
talk about the SCC with 4 DMA channels built-in.
At one point, they gave away a little shrink-wrapped package with 3
85xx parts (incl. 8530) and a booklet that gave schematics and PAL eqns
on how to interface all these parts to <insert your favourite micro
here>. The micros included 80x86, 68K, Z8K and some others (?).
> Any help/advice will be appreciated.
You're welcome! :-)
[Datclaimer: I am not a stooge for Zilog; I just like their parts.]
--
"CAUTION: OBJECTS IN SCREEN ARE CLOSER THAN THEY APPEAR"
b...@isgtec.uucp [ ..uunet!utai!lsuc!isgtec!bmw ] Bruce Walker
Uwe Kloss
In <15...@isgtec.UUCP>, Bruce M. Walker writes:
> In article <1991Sep25.1...@hemlock.cray.com> an...@aspen32.cray.com (Andy Warner) writes:
> > 2. Is there a better/cheaper 4 channel DMA chip than the 450 ?
>
> Two Zilog Z8516 DMA controllers would be better if not cheaper (although
> they may not run fast enough for you, I don't think Zilog has kept up
> with rising CPU clock rates with this part).
Choice of your chips depends much on what you want to do with it.
A nice idea which is definitely NOT generally applicable is the following:
For a real-time sampling application we needed a VERY intelligent
DMA-controller.
(No time for the MPU to set registers on and on,
multiple circular buffers and so on)
We used a MC68020 (yes MC68020, the MPU) with a short routine
which fits into the code-cache. So we were able to control
actions by only switching the contents of ONE memory cell.
I only did the soft(-ware) part of the application so really detailed
information on the hardware is not at hand.
Just thought the idea was interesting.
have fun, Uwe
--
Uwe Kloss UUCP: UweK...@lionbbs.han.de
Fasanenstrasse 65 BTX: 0531336908 0001
3300 Braunschweig FIDO: not connected
John Grana
>
>We used a MC68020 (yes MC68020, the MPU) with a short routine
>which fits into the code-cache. So we were able to control
>actions by only switching the contents of ONE memory cell.
>
VME SCSI Host Adapter that uses a 68020 to perform the DMA from an
"adjustable store" onboard buffer to VME. As Uwe states, by tuning your data
movement code (we used the movem.l instruction) to fit into the '020 cache
you can not only get pretty good data rates, but it acts like a "burst" mode
DMAC. As a side not, our VME master logic was designed to take advantage of
the move multiple instruction. Also, the data movement from the SCSI chip
(a WD33C93A) was performed by a custom ASIC that was performing 8 bit
to 32 bit data packing/bursting. We found that the 68020 was a great 32 bit
intelligent DMAC! The board supports scatter/gather, linked list, byte swap,etc.
To add new goodies, we just change the data mover logic (firmware).
>
>Just thought the idea was interesting.
>
Sure is.
--
__
John Grana, Performance Technologies Incorporated j...@pt.com
315 Science Parkway, Rochester, New York 14620 uupsi!ptsys1!jjg
Phone: (716) 256-0200 Fax: (716) 256-0791