Hi, first time here so be gentle...
I'm playing around with TTL and designing an 8 bit simple computer (following (sort of) Ben Eaters YouTube videos).
I have a DS1225AB 64k Non volatile static ram arranged as 8k x 8 bits. Which is great because I don't have to re-enter my program code and data.
I have been experiencing quite substantial voltage drops from 5v to say 4.4v
Originally since I only use 8 address bits I tied the other 5 address bits to ground directly, then tried a 1k resistor.
I also tied the control signals ~WE, ~OE and ~CE directly to the +5v rail and then to ground as needed.
So to read from the device I set the address inputs directly to the +5v rail as needed and the set ~CE to low (that is directly to ground), and ~WE directly to ground. Doing something similar for writing I can write and read to the RAM. All good.
However when I address the device using the outputs from a ring counter and with the outputs connected to 3mm LEDs via an inbuilt resistor I am getting output, but the problem is that there doesn't seem enough power to drive the led's properly. All seems fine if I manually set the address lines (directly to +5v). I seem to again get a substantial power drop. I am using a proper bench supply, though I don't how good these Chinese supplies are. It says 5v and 200mA, but the multimeter shows 4.6v when my RAM is connected and my (also Chinese) scope shows what seems to me to be a noisy power line.
So my question is? (sorry for the long preamble) How should I connect to inputs, outputs and control lines. Should I be using a resistor (1K?) to pull up or down all inputs (as for TTL) or is being tied directly to ground or 5v okay?
(Apologies if I am not providing enough info or if I should be posting in a different way)
I'm playing around with TTL and designing an 8 bit simple computer (following (sort of) Ben Eaters YouTube videos).
I have a DS1225AB 64k Non volatile static ram arranged as 8k x 8 bits. Which is great because I don't have to re-enter my program code and data.
I have been experiencing quite substantial voltage drops from 5v to say 4.4v
Originally since I only use 8 address bits I tied the other 5 address bits to ground directly, then tried a 1k resistor.
I also tied the control signals ~WE, ~OE and ~CE directly to the +5v rail and then to ground as needed.
So to read from the device I set the address inputs directly to the +5v rail as needed and the set ~CE to low (that is directly to ground), and ~WE directly to ground. Doing something similar for writing I can write and read to the RAM. All good.
However when I address the device using the outputs from a ring counter and with the outputs connected to 3mm LEDs via an inbuilt resistor I am getting output, but the problem is that there doesn't seem enough power to drive the led's properly. All seems fine if I manually set the address lines (directly to +5v). I seem to again get a substantial power drop. I am using a proper bench supply, though I don't how good these Chinese supplies are. It says 5v and 200mA, but the multimeter shows 4.6v when my RAM is connected and my (also Chinese) scope shows what seems to me to be a noisy power line.
So my question is? (sorry for the long preamble) How should I connect to inputs, outputs and control lines. Should I be using a resistor (1K?) to pull up or down all inputs (as for TTL) or is being tied directly to ground or 5v okay?
(Apologies if I am not providing enough info or if I should be posting in a different way)