Now that the power supply is running, let's build what every processor needs: a clock and reset.
As you would expect, you have many choices again when it comes to the clock section (which is all in the front, right part of the circuit board near the reset switch).
More choices! Clock frequencies and stuff
The CV runs at 3.57MHz, and we're using a crystal oscillator. You may or may not be able to find that frequency, so you can also use a crystal oscillator of twice or even 4X that frequency. The board has a built-in divider that you need to set accordingly. I am using a crystal oscillator of 14,31818 MHz in the XO53 package, which is 5x3 mm and may be a bit hard to solder. So be extra careful. Alternatively (!) you can use a canned oscillator in the 8 pin DIL package right next to it. That one you can also socket if you want to overclock your CV (why would you want to do that???). Remember, use either the XO53 or the DIL oscillator, not both!
Then solder
U20, U22 74LS74D (SO14)
R3 47 Ohms
R30, R61, R62 1k resistor
and set ONE jumper:
/4 for 14.3 MHz
/2 for 7.14 MHz
or /1 for 3.57 MHz
Solder a test point to the point marked "GROUND" near the crystal oscillator can. This ground is useful for future measurements.
Now power up and use a frequency counter (or scope) to verify 3.57 MHz at TP1
and verify 1,79 MHz at TP2
And now for reset
Once again, you have choices. You can use the stock Coleco reset switch. But if that's not an option for you, you can also use a BOURNS switch part number 1543-650-149. It is very similar, but to make it work with the ColecoVision actuator, you need to install a small washer on the switch's stud.
Classic or modern?
The next choice is the kind of reset generator. You can build the classic Coleco reset circuit using a capacitor and a resistor, or you can use a modern reset controller. I find that the Coleco circuit is not always reliable, especially when switching the unit off and on again. This is why I prefer the reset controller solution, but a purist may want to go capacitor/resistor. Anyway, for both options, you need these parts:
U18 74LS05D (SO14)
R10 1k
R11 22k
R12 1k
R13 3k3
R41 4k7
For the classic Coleco R/C reset circuit, use:
R8 1M
R9 91k
C7 1u/25V X5R
Otherwise, leave R8 and C7 unpopulated, and instead populate
U49 MAX803L/MAX803M-EUR or SGM803B-MXN3LG / -LXN3LG
R9 4k7
Again: testing
Turn on power, verify U1 pin 26 is high and goes low when pressing reset. If you have a scope, you can see Reset go from low high half a second after power-on.
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