Pulses on breadboard supply lines

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?

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).

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:

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).

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

A picture of the scope trace that shows the supply pulse might help, also.

Use a PCB !!

Signals over 100Khz is to high for a solderless breadboard.

Donald

For something like this on protoboard, I've been known to use three or four bypass capacitors on one processor. Like a 1 uF tant. in parallel with a .1 ceramic from Vcc to Gnd, and another .1 ceramic from each power pin to the opposite bus. And the buses themselves usually get at least 3, preferably about 5 or 6 of different values.

I'm sure this will start flames, but I don't believe it's possible for there to be too many bypass capacitors.

I don't think I'd try to do anything faster than a typical Z80 on a protoboard, however.

Good Luck! Rich

Idunno, I've ran PWM on the order of 25-50W on mine at that frequency. ;-)

At higher RF, signals tend not to stay in the wires anyway so I don't mess with it to begin with ;-)

Tim

-- Deep Fryer: a very philosophical monk. Website: