I'll need to get some parts I am missing to continue the build, but I was able to fully follow and replicate your first videos progress. I have two main questions: in the beginning of the video you showed some parts, will a 74IC74 work in place of the 74HC74, also for the 74HC123 would I need this exact one or would an HC in a close number range(ex. I have a 74hc138) be able to accomplish it with similar results?
Sorry for my late reply. I'm really happy to hear that you got the first part of the computer working, good job! I tried to find the data sheet for the 74LC74 but the closest I could find was the 74LCX74 which is the low power (voltage) version of the 74 series chips, which operate at (Vcc) 2.5 - 3.3V, with 5V tolerant input pins (eg CLK, D) so it would in theory (with some minor changes to circuit) be possible to use the 74LCX74, with a separate 3.3V supply just for that chip, but I would make things more complicated. So I'd really recommend using the HC and AC variants of the 74 series logic (HCT and ACT would also work) used in this project, because I've only tested it with the HC variants. So I can't guarantee that it will work with other variants. As for the 74HC123, this can't be substituted with a 74HC138 I'm afraid, because the 74HC138 is a 3 to 8 line decoder and the 74HC123 is a "dual retriggerable monostable multivibrator". So they perform completely different operations so can't be substituted with one another. The debounce circuit using the 74HC123 could be substituted with an equivalent circuit using two 555 timers (or one 556). Is the 74HC123 difficult to find? I could make an alternative debounce circuit if this is the case. Super long explanation, hope it all makes sense :)
@@DrBudgieandtheHumanMan This is super helpful! Looking around online for information was a bit difficult for me. These chips aren't to hard or expensive at all luckily. I just wanted to make sure I had the correct information before buying those smaller chips, just in case I had useable parts already! This has been a fun learning experience so far, thanks for the help! :)
you could use a cap to debounce the button but, this would restrict you to a very slow clock (a few Hz). The problem is, using just a cap you'd have to hold the preset on the 74hc74 active for the whole time the button bounce noise is present (~a few ms) and this would decide the upper limit of clock speed. But by using the debounce circuit in the video, which only holds the 74hc74 preset active for a time period in the order of pico seconds let us use the full clock speed of the Z80 (or in other words our max clock speed is no longer limited by button bounce noise). There are loads ways to debounce a button (remove noise from a signal) this is just the one they used on the Altair 8800. Hope that makes sense :)
I'll need to get some parts I am missing to continue the build, but I was able to fully follow and replicate your first videos progress. I have two main questions: in the beginning of the video you showed some parts, will a 74IC74 work in place of the 74HC74, also for the 74HC123 would I need this exact one or would an HC in a close number range(ex. I have a 74hc138) be able to accomplish it with similar results?
Sorry for my late reply. I'm really happy to hear that you got the first part of the computer working, good job! I tried to find the data sheet for the 74LC74 but the closest I could find was the 74LCX74 which is the low power (voltage) version of the 74 series chips, which operate at (Vcc) 2.5 - 3.3V, with 5V tolerant input pins (eg CLK, D) so it would in theory (with some minor changes to circuit) be possible to use the 74LCX74, with a separate 3.3V supply just for that chip, but I would make things more complicated. So I'd really recommend using the HC and AC variants of the 74 series logic (HCT and ACT would also work) used in this project, because I've only tested it with the HC variants. So I can't guarantee that it will work with other variants. As for the 74HC123, this can't be substituted with a 74HC138 I'm afraid, because the 74HC138 is a 3 to 8 line decoder and the 74HC123 is a "dual retriggerable monostable multivibrator". So they perform completely different operations so can't be substituted with one another. The debounce circuit using the 74HC123 could be substituted with an equivalent circuit using two 555 timers (or one 556). Is the 74HC123 difficult to find? I could make an alternative debounce circuit if this is the case. Super long explanation, hope it all makes sense :)
@@DrBudgieandtheHumanMan This is super helpful! Looking around online for information was a bit difficult for me. These chips aren't to hard or expensive at all luckily. I just wanted to make sure I had the correct information before buying those smaller chips, just in case I had useable parts already! This has been a fun learning experience so far, thanks for the help! :)
why not just use a capacitor to filter out the noise? or am i missing something crucial?
you could use a cap to debounce the button but, this would restrict you to a very slow clock (a few Hz). The problem is, using just a cap you'd have to hold the preset on the 74hc74 active for the whole time the button bounce noise is present (~a few ms) and this would decide the upper limit of clock speed. But by using the debounce circuit in the video, which only holds the 74hc74 preset active for a time period in the order of pico seconds let us use the full clock speed of the Z80 (or in other words our max clock speed is no longer limited by button bounce noise). There are loads ways to debounce a button (remove noise from a signal) this is just the one they used on the Altair 8800.
Hope that makes sense :)
@@DrBudgieandtheHumanMan oh thank you very much for this very detailed explanation