68040 Companion mode

68040 Companion mode

Post by Jose Sandov » Wed, 01 Feb 1995 07:08:40



Hi,

I am studying the posibility of incorporating the 68EC040(in companion mode) to a
 60360 design.
 As I was looking through the 68360 users manual I noticed that by configuring the
  360
  for MC68040 companion mode (CONFIG pins = 011), the global chip select is automat
  ically
  set to 32-bit size.  The problem is that our current design is optimized for 8-bi
  t
  boot PROM.  How can companion mode work in such a system, or will it?

  tx

  Jose


 
 
 

68040 Companion mode

Post by bo.. » Thu, 02 Feb 1995 23:27:11


|>
|>
|>
|> Hi,
|>
|> I am studying the posibility of incorporating the 68EC040(in companion mode) to a
|>  60360 design.
|>  As I was looking through the 68360 users manual I noticed that by configuring the
|>   360
|>   for MC68040 companion mode (CONFIG pins = 011), the global chip select is automat
|>   ically
|>   set to 32-bit size.  The problem is that our current design is optimized for 8-bi
|>   t
|>   boot PROM.  How can companion mode work in such a system, or will it?
|>
|>
|>   tx
|>
|>
|>   Jose
|>
|>

|>
|>

Jose,

You will either have to fake out the boot prom to look like a 32 bit
device, or boot from a 32 bit device. There is no dynamic bus-sizing
in 040 companion mode. I think Motorola makes a seperate chip to do this.

I saved a post a while back that talked about a way to hook up an 8-bit
PROM in this scenario. It is included below:

Article: 1337 of comp.sys.m68k
Path: sernews.raleigh.ibm.com!watnews.watson.ibm.com!newsgate.watson.ibm.com!news.ans.net!solaris.cc.vt.edu!news.duke.edu!concert!gatech!gt-news!prism!cc.gatech.edu!gemini.cc.gatech.edu!byron

Newsgroups: comp.sys.m68k
Subject: Re: Booting a 68000 with a single 8-bit EPROM
Date: 26 Jun 1994 16:35:37 GMT
Organization: none
Lines: 46


NNTP-Posting-Host: gemini.cc.gatech.edu
NNTP-Posting-User: byron



Quote:>Howdy! I am currently building a 68000 design and would like to boot off
>a single byte-wide EPROM instead of two byte-wide EPROMS. I have heard of
>of an implementation of this for the 68040. I'm sure it requires a custom
>PAL and a couple of latches. Any help would be greatly appreciated.

First of all I think it's more trouble than it's worth IMHO. Reason being that
any alternative solution will require more wiring and more area than the
second EPROM. Writing a byte splitter is a 15 minute excercise and many modern
eprom programmer's software have the function built in.

However some suggestions:

1) Upgrade to a 68020 or 68030 or 683XX. All of these chips have DSACKX inputs
   so that you can specify the size of the bus for each access.

2) Use a small microcontroller and a serial EEPROM. That way you can lose
   the EPROM altogether and have the microcontroller program the RAM in
   your system. Also it can provide you a reset circuit. Also since it's
   EEPROM you can build the circuit so that it's downloadable from a serial
   or parallel port and requires no erasure cycle.

3) The solution you suggested. Use a couple of 74HCT573 (or HCT373 if you like
   odd wiring) and a state machine in a GAL to do the following:

   1) Select the address with A0=0.
   2) Latch the output byte to the D15-D8 latch.
   3) Select the address with A0=1.
   4) Latch the output byte to the D7-D0 latch.
   5) Assert DTACK.

But 3) it makes it twice a slow (unless you use high speed EPROMS) and
requires quite a bit of extra ciruitry.

I'm planing on solution 2 in my next design. No EPROM just RAM and a
microcontroller (probably a PIC 16C54) and serial EEPROM solution.

Hope this helps,

BAJ
--
---
Another random extraction from the mental bit stream of...
Byron A. Jeff - PhD student operating in parallel - And Using Linux!

--
    Rodney Allen Boles

    ibm:      boles at ralvm29



 
 
 

68040 Companion mode

Post by Joel Sumn » Tue, 07 Feb 1995 03:00:38





Sandoval) writes:
> > [looking to boot 040/360 system with 8-bit EPROM]

> Jose,

> You will either have to fake out the boot prom to look like a 32 bit
> device, or boot from a 32 bit device. There is no dynamic bus-sizing
> in 040 companion mode. I think Motorola makes a seperate chip to do this.

> I saved a post a while back that talked about a way to hook up an 8-bit
> PROM in this scenario. It is included below:

[article that referred to a PAL implementation deleted]

Our group offers an appnote on how to boot a 360/040 off of an 8-bit Eprom
using a PAL.
You can obtain it from your local Motorola representative.

If you wish to have the appnote faxed to you, send e-mail to

You will receive a file that lists all of our appnotes and how to get
them.  The e-mail response gives you information on how to obtain
documents from MFAX (our fax-back service).

The basic idea of the appnote is to bring up the 360 in Master mode, copy
the PROM to SRAM, then reset the system into 040 companion mode so that
the 040 boots from SRAM.
--
Joel Sumner
Motorola Semiconductor Products
Data Communications

"When buying and selling are controlled by legislation, the first things to be bought and sold are legislators." - P.J. O'Rourke, Parliament of *s

 
 
 

1. Q: 68360 and AMUX in 68040 companion mode

I have a small PCI board which hosts an 68040 and an
68360. It plugs into a PC and uses a Spanner chip for
the PCI/68040 bridge (http://lamipc16.epfl.ch/Sm400.htm)

The 68360 is configured in 68040 companion mode. I am
using an external multiplexer for the address lines, as
shown in fig. 9-15 of the 68360 User's Manual.

I am now trying to access DRAM and have the following
problem: I cannot figure out why AMUX/BADD2/BADD3 are
tied to 5V whatever I write to PEPAR (enable AMUX) and
to GMR (GAMX=0).

The DRAM is tied to RAS4/RAS5, which seem to operate
normally. I can read/write to memory, but I can only
access a tiny portion of it.

Any help ? Any advice ? Any help would be appreciated !

        Pierre


http://diwww.epfl.ch/lami/team/arnaud/

2. My 4dos.ini

3. 68040 and 68360 companion mode

4. CONF: Web-Based Modeling and Simulation

5. Motorola 68360 running in Companion Mode

6. Mindlink

7. user mode / supervisor mode on 68000

8. Some OOP questions....

9. 68040-DX2 :-) do they exist?

10. 68040 MMU

11. Comparison between 68040/80486/ARM (ACORN RISC)/SUN SPARC/LIGHTENING

12. Wanted used 68030/68040 chips

13. 68040 mmu problem