RAM module build - part 1
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange users cite it as a real working breadboard example of 74LS189 RAM, inverters and LED outputs when troubleshooting their own builds.
Recommended by 0 people across 0 different months, 2017 to 2018.
What it is
Part 1 of Ben Eater's build of the RAM module for his breadboard 8-bit computer. It covers wiring the 74LS189 64-bit RAM chips with 74LS04 inverters and LEDs so the stored data can be seen, and lists every chip in the module.
What people said
Cites Kevin Hill · 2017-04 · Electrical Engineering Stack Exchange · on “Current limiting resistors”
On his video here: [this video] You can see that he has 8 LED's off of the 74LS04's - to indicate / watch the data being passed on the lines. I don't see any resistors, meaning that there must be a resistor in the chip?
Cites Kevin Hill · 2017-04 · Electrical Engineering Stack Exchange · on “Current limiting resistors”
In the video above - the particular portion I am referencing is right about the 5:10 mark. URL with video time mark: [this video]
Cites Anonymous · 2018-01 · Electrical Engineering Stack Exchange · on “74LS189 chip overheat”
Per your circuit description chip should not heat - there's no over-current drain, and no electrical conflicts at its outputs. If you search over internet using query "74LS189AN heating", there's a video by Ben Eater [this video] exactly on the subject, with people comments (expand the replies on that page to see them): Please, help me! When I put 3rd (WE) pin of 74LS189AN to the 5V, chip starts to heat up. Whats the problem? ... Hi! I also have this same problem and have ordered from two different ebay sellers already and they are all faulty. I cheched Jameco but they do not ship to Finland. Anyone here have any other site where these can be ordered to Finland? ... Same thing here. ordered repla
Cites Peace · 2018-02 · Electrical Engineering Stack Exchange · on “Why does a 74LS189 RAM chip light-up an LED connected to its re-inverted output when data word is HIGH while a 7489 RAM chip cannot?”
I have thought on it a lot and summarizing my confusion here. I have two SN7489N chips whose Ioh is 20uA (not sufficient to light-up an LED). Correct me if I'm wrong that Ioh is the maximum current it will draw when output is high (i.e. when memory word is a low bit in case of 7489)? On the other hand, Iol is 12mA (i.e. when memory word is a HIGH bit)? So, when I attach a hex inverter to the outputs of the 7489, which has its own Ioh and Iol readings in its datasheet, what will be my final Ioh and Iol? Also, how can a 74LS189 chip light-up an LED connected to its re-inverted output (using hex inverter) when data word is a HIGH bit while a 7489 cannot even when datasheets of both show similar
Cites Peace · 2018-02 · Electrical Engineering Stack Exchange · on “Why does a 74LS189 RAM chip light-up an LED connected to its re-inverted output when data word is HIGH while a 7489 RAM chip cannot?”
Can you please suggest me a way to be able to light-up an LED (not necessarily 7-segment display led) whose positive end is connected to the re-inverted output of 7489 when memory data (D1) is a HIGH bit? I have seen this video [this video] where he is able to light-up the LED when data word is a high bit and Vol and Iol are similar for both 7489 and 74189.
Cites Peace · 2018-02 · Electrical Engineering Stack Exchange · on “Why does a 74LS189 RAM chip light-up an LED connected to its re-inverted output when data word is HIGH while a 7489 RAM chip cannot?”
I dont think I understand the concept of input current. I always look at Ioh and Iol because I think that it is the output current during high and low output states respectively and should determine if it will light-up an LED or not (making sure that output pin is connected at right side of led as per the output state low or high). My experiment was simple. I was trying to light-up an LED using 7489 just like it lights-up in case of 74189 in Ben Eater's video ( [this video] ). But I tried everything to fail.
Cites Peace · 2018-02 · Electrical Engineering Stack Exchange · on “I have an SN7489N Memory IC which is not lighting-up an LED whose positive-end is connected to one of the output pins via a 220 Ohms resistor”
CHIP Used: SN7489N F 9013 BS [EDIT] I'm willing to light-up an LED at the output of the chip when the data stored is high, just as noted in a 74LS189 chip (and seen in this video : [this video] ). But it is only possible when I dont use any inverter and directly connect an LED's negative end to the output pin. If I use an inverter and connect the output pin to positive end of the LED, it doesn't light-up, which makes me wonder. I am using 74LS06N hex inverter.[/EDIT] [LINK] Things I've tried/made sure: a) Positive side of the LED is connected to the output and the other end to the GND (even have tried reversing it but in vain). b) Data stored is a LOW signal to get an inverted HIGH output. c) Chi