Re: ROM Cards

Brian Smithson (brian@grot.ca41.csd.mot.com)
Sat, 3 Aug 91 11:22:50 PDT

Here's the pin-out and memory map for the ROM/RAM cards. There are a few
intriguing things about this which I'll mention at the end, but the info
in the Service Manual isn't sufficient -- we're going to have to probe
with a 'scope and/or get more info from NEC.

PIN-OUT
=======

PIN SIGNAL FUNCTION
--- ------ --------
1 GND
2
3 BC Battery check
4 CD Card Signature
5 CE Card Enable
6 WE Write Enable
7 OE Output Enable
8
9
10 UB/LB Upper/Lower
11 Vcc
12 Vpp
13-20 D0-D7 Data 0 - Data 7
21
22-29 D8-D15 Data 8 - Data 15
30
31 GND
32 GND
33-48 A0-A15 Address 0 - Address 15
49 Vcc
50
51-58 A16-A23 Address 16 - Address 23
59 END
60

ROM/RAM CARD MEMORY MAP
=======================

CPU MEMORY MAP
-------------- 255

EFFFFh +---------+ ~~~
| memory | +--------+
| card |________ _ _ _ _ _ _ _ _ | bank 15| 15
| bank | | +--------+
| (64KB) | | ~~ ~~ ~~~
E0000h +---------+ | +--------+ +--------+
|_ _ _ | bank 4 | | bank 4 | 4
| +--------+ +--------+
|_ _ _ | bank 3 | | bank 3 | 3
| +--------+ +--------+
|_ _ _ | bank 2 | | bank 2 | 2
| +--------+ +--------+
|______| bank 0 | | bank 0 | 0
+--------+ +--------+
256K 1MB BANK
RAM ROM ADDRESS
CARD CARD

Here's what's intriguing:

There are 24 address lines, i.e. 16MB address space :-). That the bank
addresses go out to 256 ( 256*64KB = 16MB ) tends to confirm that it wasn't
casual that NEC defined those address lines in the pin-out; they're also in
the memory map. Ahh, to have a 16MB solid state disk on an UltraLite!

A few of the signals in the pin-out are mysterious to me.

- CD (Card Signature), I would guess, tells the UltraLite what size and/or
kind of card it is. Is it a single bit which indicates "large" or "small"
and then the writability says whether it is a ROM or RAM card? Or is it
some kind of serial stream? The former is easy to implement but would
prevent you from defining more than four types of cards: 512KB and 1MB
ROM cards, and 256KB and (as was planned at one time) 512KB RAM cards.
The latter would be more difficult to implement, but would give you a lot
of flexibility in defining card types -- and, it would allow an aftermarket
designer to create a card which was unrecognizable by the system firmware
and therefore could be handled by an aftermarket driver.

Or, perhaps, it simply tells the UltraLite whether the card is ROM or RAM,
and END is used for sizing (see below).

- UB/LB (Upper/Lower). What the heck does this mean? What is the "B" for?
Is it "upper byte / lower byte" in order to maintain some kind of
compatibility with the 8-bit bus of the 8088? I don't know enough about
those pesky i-chips to tell. After all, I work for Motorola :-). Help!

- END. Maybe this is how the cards are sized by the system. Reads or writes
of addresses out of range of the card cause the END signal to go true?

I hope this helps stir the imagination, but I think we need a good solid
technical contact at NEC. Anyone have a lead on someone like that?

-- 
-Brian Smithson
 Motorola Inc., Computer Group, Commercial Systems Division
 10700 N. De Anza Boulevard, Cupertino, CA 95014 USA, (408)366-4104
 brian@csd.mot.com, {apple | pyramid}!motcsd!brian