address

Archiver

Hello all

I just got a RAM IC that has 16 address lines, and 8 I/O lines. I want to know
how dose the address work? and is there a way to hook the stamp up to it?

Thanks
A. Conti


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Archiver

At 18:32 04/18/02, Anthony Conti wrote:
>Hello all
>
>I just got a RAM IC that has 16 address lines, and 8 I/O lines. I want to
>know how dose the address work? and is there a way to hook the stamp up to it?

You need to be a bit more specific about the chip you have because there
are surely more signals to/from this thing than address and data
lines. What's the part number? Which Stamp do you have?

The answer, short, simple, and maybe missing something, is that you don't
have enough I/O on your Stamp to drive this thing directly to it's full
capability, but if you feed the address serially to a pair of 74HC595 chips
you can output a 16-bit address using I think 2 Stamp pins. If you can't
spare 8 pins for the data, you can play similar games with other chips, but
you need one chip for input and one for output, again at a cost of only 2
pins. Then you need a pin to select the chip and one to tell it whether
you're reading or writing.

That's the general idea. I'm sure others can fill in more details if
you'll name the chip specifically.


Jim H

Archiver

>You need to be a bit more >specific about the chip you have >because there
>are surely more signals to/from >this thing than address and data
>lines. What's the part number? >Which Stamp do you have?

The Chip is A "NEC" P/N D431000ACZ

http://www.ic.nec.co.jp/memory/pdfs/M11657EJBV0DS00.pdf

This chip is large in size (memory), and I got it free so I would like to try to
use it. I am using A BS2p

Thanks
A. Conti



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Archiver

At 23:53 04/18/02, Anthony Conti wrote:

> >You need to be a bit more >specific about the chip you have >because there
> >are surely more signals to/from >this thing than address and data
> >lines. What's the part number? >Which Stamp do you have?
>
>The Chip is A "NEC" P/N D431000ACZ
>
>http://www.ic.nec.co.jp/memory/pdfs/M11657EJBV0DS00.pdf
>
>This chip is large in size (memory), and I got it free so I would like to
>try to use it. I am using A BS2p
>
>Thanks
>A. Conti

Anthony,

A 74HC595 chip can be used as a serial-to-8bit parallel device and two of
these can be cascaded to provide a 16-bit address all at the expense of
three stamp pins and use of the Shiftout instruction.

Same deal for 8 bits of input using the 74LS165. Total of 6 pins used so far.

A basic circuit using a 74HC595 is in the manual as Note #2 in the BS2
section on the Shiftin/Shiftout instructions. I'm sure someone on this
list has a more complete schematic on a website, and probably code to go
with it.

Generally speaking, to interface to your RAM, you need to "shiftout" an
address to your 74HC595 chips, "shiftout" the data if you're writing,
activate the address and data interface chips to apply the address and data
to the RAM, then set the Write Enable pin to either read or write, then
activate a Chip Select pin to activate the RAM, then if you're reading you
need to "shiftin" the data being read. When you're done, deselect the RAM
and the interface chips. Repeat as necessary.

The date sheet for the RAM describes the pinout on page 3 and the
combination of pins needed for various desired states on page 7. The
sequence of operations is shown graphically elsewhere, I forget the page.

If this still sounds interesting, but you need more details, I'm afraid
someone else who has more hands-on experience with the Stamp will need to
supply them.

Jim H

Archiver

>If this still sounds interesting, but you need more >details, I'm afraid
>someone else who has more hands-on >experience with the Stamp will need to
>supply them.

>Jim H

Thank you Jim, but I do not understand how address work. Is it that:

address slot 1, I can store a 8 bit value.
address slot 2, I can store a 8 bit value.
address slot 3, I can store a 8 bit value.
Ect.

Is this the way address work?

Thanks
A. Conti


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Archiver

A memory device is organized by address and contents at that address.
Different organizations are available. Let take fo example a simple one
that is labelled 16X8. This would mean that there are 16 separate
addresses whose locations would be listed in binary or 0001 0010 0011
-- up to 1111. At each of those 16 addresses you would have the
potential of storing 1 byte, 2 nibbles, or 16 bits. RAM chips usually
have an I/O bus where as the info of those 8 bits are stored or
retrieved. They usually have a R/W line which is going to determine at
a point in the cycle if info is going to be written to the RAM or read
from the RAM. There is also typically going to be one or more chip
enable lines, which is just as it sounds they enable the chip. And
there maybe more lines of control. All the control lines are referred
to as a control bus. RAM chips that are serial in nature, do the same
kind of things, but this info for the address, data and control maybe
all transferred to the chip over a single serial line. I taught this
stuff for 15+ years and I could probably ramble on for at least another
hour, but I think I will stop here and see what kind of questions you
might have. I would recommend doing a google search for digital
electronics, RAM organization, or just get the data sheet for the chip
you are interested in. Sometimes, if the moon is right, you will get
lucky, LIKE ME, and find an apps engineer who knows enough about his
subject to make it clear to some one who is just learning.

HTH,

Leroy

Anthony Conti wrote:
>
> >If this still sounds interesting, but you need more >details, I'm afraid
> >someone else who has more hands-on >experience with the Stamp will need to
> >supply them.
>
> >Jim H
>
> Thank you Jim, but I do not understand how address work. Is it that:
>
> address slot 1, I can store a 8 bit value.
> address slot 2, I can store a 8 bit value.
> address slot 3, I can store a 8 bit value.
> Ect.
>
> Is this the way address work?
>
> Thanks
> A. Conti
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
>
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Archiver

At 18:36 04/19/02, Anthony Conti wrote:
> >If this still sounds interesting, but you need more >details, I'm afraid
> >someone else who has more hands-on >experience with the Stamp will need to
> >supply them.
>
> >Jim H
>
>Thank you Jim, but I do not understand how address work. Is it that:
>
>address slot 1, I can store a 8 bit value.
>address slot 2, I can store a 8 bit value.
>address slot 3, I can store a 8 bit value.
>Ect.
>
>Is this the way address work?

Yes, exactly. And the 17 address lines on your RAM chip (A0 - A16)
represent 131,072 addresses, or in computer math 128K.

I just noticed I wasn't paying close enough attention earlier so I didn't
notice you had 17 address lines instead of 16. So two 8-bit
serial-to-parallel chips won't address all of your RAM; you'll need three -
or else dedicate one more Stamp pin to the task. Two chips will address
64K, half your RAM. If you go ahead, you might consider putting the 17th
line on a separate Stamp pin (or a dip switch) and have two banks of 64K,
either switched by software or manually. Or if 64K is enough, just tie the
17th address line (A16) low - to ground.

Jim H