hi everyone,
I am getting a strange reading from my oscilliscope when i probe the data pins on my memory chip. The address lines are connected to the address lines of a z80A CPU, the data lines of the chip dont connect to anything. WE is held high (as im using it as a ROM), CE is connected to a 74139 decoder and the OE is connected to the z80's RD.
I checked all the control lines + address lines, all perfect square waves. I check the add lines on the mem chip, same result. I probe the data lines and i should see random square waves (because of the different data) but instead i get a continuous wave that has an odd shape.
The wave has half a square wave but instead of falling to 0 quickly it decays till its 0 and then goes back up, so think of half a square wave and then a capacitor exponent decay at the end.
http://mientki.ruhosting.nl/data_www/pic/jalss/rcx_motor_display2.gif
looks just like the second one :<
I forgot to put by pass capacitors so i added them, same result
I made sure no pins where floating, same result
If i slow the clock down from the usual ~900 KH down to HZ it works and the data lines display what they should be doing.
I checked the CLK line from the 4093 and its a clean square wave. Power lines have no fluctuation. I tried different memory chips and different z80 but the problem still persist
I am getting a strange reading from my oscilliscope when i probe the data pins on my memory chip. The address lines are connected to the address lines of a z80A CPU, the data lines of the chip dont connect to anything. WE is held high (as im using it as a ROM), CE is connected to a 74139 decoder and the OE is connected to the z80's RD.
I checked all the control lines + address lines, all perfect square waves. I check the add lines on the mem chip, same result. I probe the data lines and i should see random square waves (because of the different data) but instead i get a continuous wave that has an odd shape.
The wave has half a square wave but instead of falling to 0 quickly it decays till its 0 and then goes back up, so think of half a square wave and then a capacitor exponent decay at the end.
http://mientki.ruhosting.nl/data_www/pic/jalss/rcx_motor_display2.gif
looks just like the second one :<
I forgot to put by pass capacitors so i added them, same result
I made sure no pins where floating, same result
If i slow the clock down from the usual ~900 KH down to HZ it works and the data lines display what they should be doing.
I checked the CLK line from the 4093 and its a clean square wave. Power lines have no fluctuation. I tried different memory chips and different z80 but the problem still persist