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bonzer
Guest
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 Posted:
Mon Dec 12, 2005 1:35 am Post subject:
Pulses on breadboard supply lines |
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I have been put together a circuit on solderless breadboard that links
a z80 to my pc serial port. I ran a program that continually sends data
from the pc and the z80 circuit echoes it back so I can see that it
works ok. The problem is that characters being sent are sometimes being
corrupted. If I put my logic probe on the ground lines off the
breadboard, a pulse on the ground line is heard at the same time a
character is corrupted. I'm assuming it's these pulses on the ground
lines that are causing a mis-read of data. The data is only being read
and transmitted at 9600bps.
How can I get rid of these glitches?
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John Popelish
Guest
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Mon Dec 12, 2005 1:35 am Post subject:
Re: Pulses on breadboard supply lines |
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Is the Z80 supply bypassed with a capacitor very close to the
processor? What other chips are involved in this circuit? What is
the source of power? |
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bonzer
Guest
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Mon Dec 12, 2005 9:35 am Post subject:
Re: Pulses on breadboard supply lines |
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The z80 does have a capacitor across the line near it. There are two
breadboards that are linked. The first has the Z80, an eprom, some ram
and a few logic ic's and the second board has a Zilog SIO/0, a CTC and
max232 ic on it. The source of the power to both boards is a PC ATX
power supply (5v).
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Tim Williams
Guest
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Mon Dec 12, 2005 2:16 pm Post subject:
Re: Pulses on breadboard supply lines |
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Idunno, put on more caps? LOL
Electrolytics with low ESR, like removed from switching supplies, might
help. Not that contact resistance helps that any, but that shouldn't matter
too much. (I've pulled 20A through them protoboard rails and it seems okay
with it!)
Tim
--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms |
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John Popelish
Guest
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| Posted:
Mon Dec 12, 2005 5:35 pm Post subject:
Re: Pulses on breadboard supply lines |
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bonzer wrote:
| Quote: | John, the supply is clean most of the time EXCEPT when there's a LOT of
switching activity - ie, transferring lots of data on the serial line.
I will try to get some pics of the board(s).
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A picture of the scope trace that shows the supply pulse might help, also. |
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bonzer
Guest
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| Posted:
Mon Dec 12, 2005 5:35 pm Post subject:
Re: Pulses on breadboard supply lines |
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John, the supply is clean most of the time EXCEPT when there's a LOT of
switching activity - ie, transferring lots of data on the serial line.
I will try to get some pics of the board(s). |
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John Popelish
Guest
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| Posted:
Mon Dec 12, 2005 5:35 pm Post subject:
Re: Pulses on breadboard supply lines |
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bonzer wrote:
| Quote: | The z80 does have a capacitor across the line near it. There are two
breadboards that are linked. The first has the Z80, an eprom, some ram
and a few logic ic's and the second board has a Zilog SIO/0, a CTC and
max232 ic on it. The source of the power to both boards is a PC ATX
power supply (5v).
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Is the supply clean if you load it with just a resistor that draws the
same average current as your circuit?
A picture or three of your assembly might be helpful. Do you have
place on the web to post a few? Do you have an ISP that allows you to
post pictures through the newsgroup,
alt.binaries.schematics.electronic |
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neon
Joined: 25 Feb 2006
Posts: 586
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Fri Mar 03, 2006 1:55 pm Post subject:
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| PUT A MYLAR .1MFD across each chip. check your gnd you might have a ground loop situation since there are 2 boards involved. make the ground solid. i hate say it but sometimes you need a power amp to regenarate the gnd that is the last resort though. take care. |
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