<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<title></title>
</head>
<body bgcolor="#ffffff" text="#000000">
The /CS signal is /CS_RAM. The write /WR is to RAM.<br>
<br>
However, the /RD is the instruction fetch from ROM. The
instruction to store to 8000h is 3 bytes long. The /OE without
/CS_RAM is correct, since I take it your program is in ROM. /CS_ROM
should be asserted during these byte reads, not /CS_RAM, which is
the scope display.<br>
<br>
Move the /CS probe to /CS_ROM, and I bet you'll see the /CS on the
previous /OE pulses and not on the /WE pulse.<br>
<br>
--John<br>
<br>
<br>
<br>
<br>
<br>
On 09/25/2013 05:41 AM, Max Scane wrote:
<blockquote
cite="mid:CADv-vybnjVya+03qGt_-dZzcTx0Cdqm8SK0RFPY5_6vg=sh0zw-JsoAwUIsXosN+***@public.gmane.org"
type="cite">
<div dir="ltr">
<div>Hi Wayne,</div>
<div><br>
</div>
Well that is interesting. It looks like your write logic is
working fine, /CS and /WE are asserted at the same time which is
correct.
<div><br>
</div>
<div>However, the read logic seems to be incorrect. /CS and /OE
should be asserted at the same time much like the write
sequence.</div>
<div><br>
</div>
<div>/CS enables the RAM chip and activates its address lines.
When /OE goes low the data from the RAM cells is put on the
data bus. Without /CS, the RAM won't do a thing.</div>
<div><br>
</div>
<div>The question now is why is /CS not asserted during a read
of RAM. We know that the read logic works for ROM because you
can execute a program</div>
<div> correctly.<br>
</div>
<div><br>
</div>
<div>Looking at the schematic, if we work back from the RAM chip
along the /CS path, we have a DS1210. We know that is OK
because we get /CS when writing.</div>
<div><br>
</div>
<div>
Further back we have U15 (RAM/ROM Memory Decode Logic) this
is where /CS_RAM is generated). </div>
<div><br>
</div>
<div>/CS_RAM is generated when /MREQ , (Z80 signal saying we are
doing a memory operation rather than an IO operation) and A15
is high (8000h - FFFFh) or when when /MREQ is asserted and
the ROM is disabled.(RAM at 0-FFFF)</div>
<div><br>
</div>
<div>So at power up, ROM is enabled, therefore /CS_RAM will only
be asserted when we are doing a memory operation and the
address is 8000h or above.</div>
<div><br>
</div>
<div>That sounds about right I think.</div>
<div><br>
</div>
<div>Still no explanation why you can't read from RAM though.</div>
<div><br>
</div>
<div>First things first.</div>
<div><br>
</div>
<div>1. Check your program, make sure you are writing to 8000h
and not somewhere else. The hex code should be 32 00 80.</div>
<div>2. Maybe try writing to other locations above 8000h.</div>
<div><br>
</div>
<div>I hope that makes sense (been a long day)</div>
<div>Let us know how you go with that.</div>
<div><br>
</div>
<div>Cheers!</div>
<div><br>
</div>
<div>Max</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Wed, Sep 25, 2013 at 9:30 PM,
opticpow <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:wayne-***@public.gmane.org" target="_blank">wayne-***@public.gmane.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div dir="ltr">Hi Max,<br>
<br>
With that same program, here is a capture of those
signals. What seems interesting is that according to your
description, shouldn't /OE be low, as both /CE & /WE
are asserted in the attached screenshot?<br>
<br>
Wayne.
<div class="im"><br>
<br>
On Wednesday, September 25, 2013 8:43:18 AM UTC+10, Max
Scane wrote:</div>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div dir="ltr">
Hi Wayne,
<div><br>
</div>
<div class="im">
<div>On the ram chip have a look at the following
signals:</div>
<div><br>
</div>
<div>Pin 24 /OE This is the Output Enable, it is
asserted during a read</div>
<div>Pin 22 /CS This is the Chip Select, it is
asserted during an Read or Write</div>
<div>Pin 29 /WE This is the Write Enable, it is
asserted during a Write</div>
<div><br>
</div>
<div>Another thing to look at is the DS1210 chip as
it controls access to the RAM chip.</div>
<div><br>
</div>
<div>Cheers!</div>
</div>
</div>
<div>
<div class="h5">
<div><br>
<br>
<div class="gmail_quote">On Tue, Sep 24, 2013 at
11:18 PM, opticpow <span dir="ltr"><<a
moz-do-not-send="true">wa...-***@public.gmane.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:
0pt 0pt 0pt 0.8ex; border-left: 1px solid
rgb(204, 204, 204); padding-left: 1ex;">
<div dir="ltr">Hi Max,<br>
<br>
Attached is a high res of my board. <br>
<br>
1. All jumpers are in the default positions,
except for K6 & K8, as I'm using Flash
ROM (29F040)<br>
2. As above. Did double check<br>
3. I have two RAM chips, both identical (you
can see one clearly in the pic) both give
the same result. I'd doubt both would be
faulty / damaged?<br>
4. Done:<br>
<br>
<div style="margin-left: 40px;"><font
size="1">
<div>start:<br>
ld a,0ffh ; ->
Put all ones in the accumulator<br>
ld (8000h),a ; -> Store
the contents of the accumulator at the
specified location<br>
</div>
nop<br>
nop
<div><br>
ld a,(8000h) ; -> Load
the contents of the specified memory
location in the accumulator<br>
</div>
nop<br>
nop<br>
jp start ; -> Jump back
to beginning if actual = expected<br>
end<br>
</font></div>
<br>
5. /WR is wiggling between 4.1 & 4.5MHz
with the above code. I could not see a CS on
the schematic for the RAM chip, I did see
/CS on pin 5 of the DS1302. Is this what you
mean? I see no activity on pin 5 with above
program running.<br>
<br>
Thanks for you help.<br>
<br>
Wayne.
<div><br>
<br>
<br>
On Monday, September 23, 2013 8:44:54 PM
UTC+10, Max Scane wrote:</div>
<blockquote class="gmail_quote"
style="margin: 0pt 0pt 0pt 0.8ex;
border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div dir="ltr">
<div>Hi Wayne,
<div><br>
</div>
<div>8000h is the first accessible ram
address. Upon power on the ROM is
switched into the first 32KB so you
have ROM at 0000-7FFF and RAM at
8000-FFFF. The test result looks
like you can't access/write to the
RAM.</div>
<div><br>
</div>
<div>I would check the following:</div>
<div><br>
</div>
<div>1. Check RAM jumper</div>
<div>2. Check MCPL jumpers (set to
default)</div>
<div>3. Replace RAM chip</div>
<div>4. Modify program to continuously
loop reading/writing to RAM</div>
<div>5. Check with CRO or Logic probe
for activity on the CS and /WR pins
on the RAM </div>
<div><br>
</div>
<div>Jumper settings can be found at:</div>
<div><a moz-do-not-send="true"
href="http://n8vem-sbc.pbworks.com/w/page/39172478/N8VEM%20SBC%20V2%20Jumper%20Settings"
target="_blank">http://n8vem-sbc.pbworks.com/w/page/39172478/N8VEM%20SBC%20V2%20Jumper%20Settings</a><br>
</div>
<div><br>
</div>
<div>I hope this helps.</div>
<div><br>
</div>
<div>Regards,</div>
<div><br>
</div>
<div>Max</div>
<div><br>
</div>
</div>
<div><br>
<br>
<div class="gmail_quote">
<div>On Mon, Sep 23, 2013 at 8:02
PM, opticpow <span dir="ltr"><<a
moz-do-not-send="true">wa...-***@public.gmane.org</a>></span>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin: 0pt 0pt 0pt 0.8ex;
border-left: 1px solid rgb(204,
204, 204); padding-left: 1ex;">
<div>
<div dir="ltr">Hi All,<br>
<br>
It has been a bit of a while
(well long while actually) but
life and all that!<br>
<br>
Anyway, I have a new shed,
I've cracked out the the ol'
sbcv2 and I'm debugging again.
Current status is that scream
works (lots of zeros). Next
test I've tried is this code
(I believe John C suggested
this):<br>
<br>
start:<br>
ld a,0ffh ;
-> Put all ones in the
accumulator<br>
ld (8000h),a ;
-> Store the contents of
the accumulator at the
specified location<br>
ld a,(8000h) ;
-> Load the contents of the
specified memory location in
the accumulator<br>
cp 0ffh ;
-> Compare actual with
expected<br>
jp z,start ;
-> Jump back to beginning
if actual = expected<br>
halt ;
-> actual did not match
expected so halt<br>
end<br>
<br>
<br>
Running this give me a Red
Halt on the led, so I guess
there is an issue with the
RAM. I've been studying the
schematic, but I'm not quite
sure which of the chips would
be required for this process.
I'm guessing not the extended
addressing logic so maybe:<br>
<br>
U23 (obviously)<br>
U21<br>
and U4 U14 U6 from the IO
decode logic??<br>
<br>
Thanks,<br>
<br>
Wayne.<span><font
color="#888888"><br>
</font></span></div>
</div>
<span><font color="#888888">
<div>
-- <br>
You received this message
because you are subscribed
to the Google Groups "N8VEM"
group.<br>
</div>
To unsubscribe from this group
and stop receiving emails from
it, send an email to <a
moz-do-not-send="true">n8vem+un...-/***@public.gmane.org</a>.<br>
To post to this group, send
email to <a
moz-do-not-send="true">n8...-/***@public.gmane.org</a>.
<div><br>
Visit this group at <a
moz-do-not-send="true"
href="http://groups.google.com/group/n8vem"
target="_blank">http://groups.google.com/group/n8vem</a>.<br>
For more options, visit <a
moz-do-not-send="true"
href="https://groups.google.com/groups/opt_out"
target="_blank">https://groups.google.com/groups/opt_out</a>.<br>
</div>
</font></span></blockquote>
</div>
<br>
</div>
</div>
</blockquote>
</div>
<div>
<div>
-- <br>
You received this message because you are
subscribed to the Google Groups "N8VEM"
group.<br>
To unsubscribe from this group and stop
receiving emails from it, send an email to
<a moz-do-not-send="true">n8vem+un...-/***@public.gmane.org</a>.<br>
To post to this group, send email to <a
moz-do-not-send="true">n8...-/***@public.gmane.org</a>.<br>
Visit this group at <a
moz-do-not-send="true"
href="http://groups.google.com/group/n8vem"
target="_blank">http://groups.google.com/group/n8vem</a>.<br>
For more options, visit <a
moz-do-not-send="true"
href="https://groups.google.com/groups/opt_out"
target="_blank">https://groups.google.com/groups/opt_out</a>.<br>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<div class="HOEnZb">
<div class="h5">
-- <br>
You received this message because you are subscribed to
the Google Groups "N8VEM" group.<br>
To unsubscribe from this group and stop receiving emails
from it, send an email to <a moz-do-not-send="true"
href="mailto:n8vem%2Bunsubscribe-/***@public.gmane.org"
target="_blank">n8vem+unsubscribe-/***@public.gmane.org</a>.<br>
To post to this group, send email to <a
moz-do-not-send="true"
href="mailto:n8vem-/***@public.gmane.org" target="_blank">n8vem-/***@public.gmane.org</a>.<br>
Visit this group at <a moz-do-not-send="true"
href="http://groups.google.com/group/n8vem"
target="_blank">http://groups.google.com/group/n8vem</a>.<br>
For more options, visit <a moz-do-not-send="true"
href="https://groups.google.com/groups/opt_out"
target="_blank">https://groups.google.com/groups/opt_out</a>.<br>
</div>
</div>
</blockquote>
</div>
<br>
</div>
-- <br>
You received this message because you are subscribed to the Google
Groups "N8VEM" group.<br>
To unsubscribe from this group and stop receiving emails from it,
send an email to <a class="moz-txt-link-abbreviated" href="mailto:n8vem+unsubscribe-/***@public.gmane.org">n8vem+unsubscribe-/***@public.gmane.org</a>.<br>
To post to this group, send email to <a class="moz-txt-link-abbreviated" href="mailto:n8vem-/***@public.gmane.org">n8vem-/***@public.gmane.org</a>.<br>
Visit this group at <a moz-do-not-send="true"
href="http://groups.google.com/group/n8vem">http://groups.google.com/group/n8vem</a>.<br>
For more options, visit <a moz-do-not-send="true"
href="https://groups.google.com/groups/opt_out">https://groups.google.com/groups/opt_out</a>.<br>
</blockquote>
</body>
</html>
<p></p>
-- <br />
You received this message because you are subscribed to the Google Groups "N8VEM" group.<br />
To unsubscribe from this group and stop receiving emails from it, send an email to n8vem+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/***@public.gmane.org<br />
To post to this group, send email to n8vem-/JYPxA39Uh5TLH3MbocFF+G/***@public.gmane.org<br />
Visit this group at <a href="http://groups.google.com/group/n8vem">http://groups.google.com/group/n8vem</a>.<br />
For more options, visit <a href="https://groups.google.com/groups/opt_out">https://groups.google.com/groups/opt_out</a>.<br />