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PostPosted: Fri Mar 09, 2018 8:03 pm 
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Testing the functions of Pins 4, 5 and 22

Test 1: Connect a LED to Pin 22. Do the $4101/$4100 write sequence (#1: $4102=$30, $4101=$10, $4100=xx. #2: $4102=$30, $4101=$20, $4100=xx) and see if the LED changes.
Test 2: Swap the connections of Pins 4 and 5 from GND/Vcc to Vcc/GND and see if the way the LED change is now reversed. (I'm not sure if this can be done with wire-wrap?)

I think you wrote that you connected a LED to Pin 22 before, but as I understand your posts, you had not done the $4101 write sequence correctly before.

@MLX: Can you check on a Mapper 173 board (Xiao Mali or F-15 City War) if Pin 6 is indeed unconnected or connected underneath the ITC IC to some other pin (possibly also Pin 19)?


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PostPosted: Fri Mar 09, 2018 10:25 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
NewRisingSun wrote:
Test 1: Connect a LED to Pin 22. Do the $4101/$4100 write sequence (#1: $4102=$30, $4101=$10, $4100=xx. #2: $4102=$30, $4101=$20, $4100=xx) and see if the LED changes.
Bright side: Your hypothesis is at least mostly correct; pin 22 is definitely ... at least approximately ... a latched copy of pin 12 on writes to $4101. It changes immediately on writes to $4101; no need to write to any other register.

Down side: Pin 22 on my IC emits a variety of different high frequency signals.

My initial test consisted of four "old" LEDs, connected in series, from +5V to ground. None light. I then connect the middle leg (two LEDs both above and below) to the pin and ... somehow all four LEDs light up in different brightnesses.

Well, that's odd. Oscilloscope time!

... That's worse. Pin 22 is some logical function of other pins, depending on what value was latched to $w4101/pin12. I spent some time comparing it to other pins and it wasn't obviously the same as anything else. It is more-or-less synchronous, however.

... I tentatively think, that when the value written to pin 12 is 0, the resulting signal is pin 6 OR pin 8.
... and that when the value latched is 1, the resulting signal is just pin 8?

Using wire wrap, I'd connected CPU D0-D2,D6 to pins 6, 8, 9, 10 as I specified in the pinout—the code in Policeman doesn't care.

Pins 8 and 9 (what I've connected to D1 and D2) is definitely unequivocally latched via $4102 and can be read back immediately. Pin 6 isn't latched on writes to $4102—instead it seems that 0 is always latched, but the value read back is inverted according to the invert bit in $4101. (In other words, pin 6 reads back the inverted value latched into pin 12)

... and I realize now that I completely forgot to play around with what writes to $4103 did, if anything, to any of the above.

Quote:
Test 2: Swap the connections of Pins 4 and 5 from GND/Vcc to Vcc/GND and see if the way the LED change is now reversed. (I'm not sure if this can be done with wire-wrap?)
That definitely requires desoldering.

Also, just in case anyone else is tempted: DON'T do this before making sure that pins 4 and 5 are not internally connected to pins 7 and 19. If you connect 5V across the bond wires and a silicon trace inside that'll assuredly blow something up.


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PostPosted: Sun Mar 11, 2018 3:14 am 
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Pin 6 is totally unconected. Also if I put the positive electrode on pin 6 only 7, 8 (=19) give some continuity result while most will if pin 6 is negative.


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PostPosted: Sun Mar 11, 2018 4:26 am 
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lidnariq wrote:
That definitely requires desoldering.
Would you be willing to do such a thing and run tests if I purchase the offered Xiao Mali cartridge from MLX and reimburse him for shipping it to you?


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PostPosted: Sun Mar 11, 2018 5:39 am 
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Economy shipping (2 weeks to 1 month) is cheap. I don't mind paying that. But if you want to get it in 10 days, that's different.


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PostPosted: Sun Mar 11, 2018 10:59 am 
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Location: Seattle
Yeah, sure, I'm willing to desolder a chip and set up a less cranky testbed. I'm in no rush.


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