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1-wire specification

R

Raveninghorde

Jan 1, 1970
0
I am using a DS2438 as a battery monitor. The app notes recommend a
series 330 ohm in the DQ line for static protection. The data sheet
shows 4k7 as the master pull up resistor.

I have a Link45 serial to 1-wire interface and the cooms does not
work. A quick check shows a 1k bus pull up. So the 330 ohm is not
allowing the output from the battery to get lower than about 1.2V.

Is there actually a specified min and max for the bus pull up
resistor. I.m looking but haven't found a specification yet.
 
R

Raveninghorde

Jan 1, 1970
0
330 Ohms would imply something like 2.2K _minimum_ pull-up.

...Jim Thompson

Your math isn't too bad ;-)

I am seeing Maxim app notes for 1-wire on long cables saying 1k may be
needed. This of course doesn't work with the Maxim app notes saying
fit a 330 ohm resistor for static protection. So it looks like I have
to design for 1k pull up. Just wish I could find a spec giving min
and max figures.

Who writes app notes? Certainly no one who knows what they are doing.
 
M

Mark Zenier

Jan 1, 1970
0
WangoTango said:
I still remember the convoluted spec on the NMOS MC68705P3S port A.
I went something like this :

"The PORT A pull up option, available on the masked part, is not
optional on the ceramic (CS) part"

OK, does that mean it is always in place, or not available?
When I called the regional FAE he didn't know either.

Should be buried in the spec sheet somewhere. Dig, dig, dig ...
ADI-1031, October, 1984.

Compare the 6805P2 and 68705P3 "Port DC Characteristics" pages in the
back. There's only one section for the 705P3 Port A characteristics.
But for the P2, there are two. So find the one that's the best match.
"Iih" for Port A in the 705P3 matched the characteristics of "Iih"
for port A on the the P2 "with CMOS Drive Enabled". So, always enabled.

Took me about 5 minutes to answer a question that's 25 years obselete. ;-)

Mark Zenier [email protected]
Googleproofaddress(account:mzenier provider:eskimo domain:com)
 
M

Mark Zenier

Jan 1, 1970
0
The point was that there should be a bit more clarity to begin with, not
that the question couldn't be answered with some digging.

And, shouldn't there be TWO listing for PORTA also?
One for the masked part when the customer opts for the optional option
and one for when they don't? :)

I thought that's what I said. " But for the P2, there are two. "
Meaning, they have two sections in the MC6805P2 (and 'P4 and 'P6)
"Port DC Electrical Characteristics" table of the spec sheet, one
for "Port A with CMOS Drive enabled", and one for "Port C and
Port A with CMOS Drive Disabled". Giving VOL, VOH, VIL, and VIH
under various conditions. The "drive enabled" section matches
the '705P3' table in having both the additional "VOH with a 10 uA load"
spec, and having the higher IIH spec.

Mark Zenier [email protected]
Googleproofaddress(account:mzenier provider:eskimo domain:com)
 
J

Jon Kirwan

Jan 1, 1970
0
I thought that's what I said. " But for the P2, there are two. "
Meaning, they have two sections in the MC6805P2 (and 'P4 and 'P6)
"Port DC Electrical Characteristics" table of the spec sheet, one
for "Port A with CMOS Drive enabled", and one for "Port C and
Port A with CMOS Drive Disabled". Giving VOL, VOH, VIL, and VIH
under various conditions. The "drive enabled" section matches
the '705P3' table in having both the additional "VOH with a 10 uA load"
spec, and having the higher IIH spec.

Mark Zenier [email protected]
Googleproofaddress(account:mzenier provider:eskimo domain:com)

Mark, I think your answer was tight and targeted at the OP's
first post well. I think Asgard24's response tried to change
the subject, writing "The point was that there should be a
bit more clarity to begin with, not that the question
couldn't be answered with some digging." That hadn't been
the OP's point, but it was a point Asgard24 tried to turn it
into for reasons I don't fathom well.

You were right to write as you did. It was on point and
nicely said.

Jon
 
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