Thank you for the warm welcome and all your answers with hints!
@Dr Jefyll
Quote:
Welcome, HelgeCPH. For some reason I'm not able to view the image. May I suggest you attach it with your post? This forum (unlike many others) does allow that.
Right, I do not know why this happens, but I edited the post and added the illustration as attachement.
Quote:
I agree with Ed. You need to find out why SYNC appears to be remaining low. Are you *sure* the RDY pin is being pulled up? You can verify that with just a voltmeter.
Unfortunately, I do not have a proper voltmeter either. But I did what you suggested with the help of an LED, just to see if pins are high/low as expected.
When doing that, I figured out that my problem was really easy to solve, stupid, and I should have seen it before posting...
In the schematics I connected the clock signal to pin `53` of the Arduino. However, in my sketch I set the clock pin to `52`. That of course meant that there was no real clock signal coming to the MPU. In connection with the `loop` of the sketch I was mislead to that a clock signal was properly generated.
As I understand, the clock pin was floating and therefore something seemed to be happening anyways only with in weird steps. Is that understanding right?
@hoglet
Quote:
My money is on insufficient decoupling capacitors. They need to be physically as close to the power pins of the 65C02 as possible. As well as a 0.1uF ceramic, I would add a 10uF electrolytic.
Since I do not really know electronics, I have to ask here. Do I understand it correctly, that you suggest to add one leg of a decoupling capacitor to VDD (pin 8 of the MPU) and the other one of to ground? This is how I understand decoupling capacitors should be used but I am not sure if it is right.
Just for completeness an excerpt of the log in which now the SYNC signal is alternating, the address lines "count" properly, and in which the reset is properly visible via the addresses $FFFC and $FFFC
Code:
11101011 01111111 : 0xEB 0x7F RWB: 1 SYNC: 1
11101011 10000000 : 0xEB 0x80 RWB: 1 SYNC: 0
11101011 10000000 : 0xEB 0x80 RWB: 1 SYNC: 1
11101011 10000001 : 0xEB 0x81 RWB: 1 SYNC: 0
11101011 10000001 : 0xEB 0x81 RWB: 1 SYNC: 1
11101011 10000010 : 0xEB 0x82 RWB: 1 SYNC: 0
11101011 10000010 : 0xEB 0x82 RWB: 1 SYNC: 1
11101011 10000011 : 0xEB 0x83 RWB: 1 SYNC: 0
11101011 10000011 : 0xEB 0x83 RWB: 1 SYNC: 1
11101011 10000100 : 0xEB 0x84 RWB: 1 SYNC: 0
11101011 10000100 : 0xEB 0x84 RWB: 1 SYNC: 1
11101011 10000101 : 0xEB 0x85 RWB: 1 SYNC: 0
11101011 10000101 : 0xEB 0x85 RWB: 1 SYNC: 1
11101011 10000110 : 0xEB 0x86 RWB: 1 SYNC: 0
11101011 10000110 : 0xEB 0x86 RWB: 1 SYNC: 1
11101011 10000111 : 0xEB 0x87 RWB: 1 SYNC: 0
11101011 10000111 : 0xEB 0x87 RWB: 1 SYNC: 1
11101011 10001000 : 0xEB 0x88 RWB: 1 SYNC: 0
11101011 10001000 : 0xEB 0x88 RWB: 1 SYNC: 1
11101011 10001001 : 0xEB 0x89 RWB: 1 SYNC: 0
11101011 10001001 : 0xEB 0x89 RWB: 1 SYNC: 1
11101011 10001010 : 0xEB 0x8A RWB: 1 SYNC: 0
11101011 10001010 : 0xEB 0x8A RWB: 1 SYNC: 1
11101011 10001011 : 0xEB 0x8B RWB: 1 SYNC: 0
11101011 10001011 : 0xEB 0x8B RWB: 1 SYNC: 0
11101011 10001011 : 0xEB 0x8B RWB: 1 SYNC: 0
11101011 10001011 : 0xEB 0x8B RWB: 1 SYNC: 0
11101011 10001011 : 0xEB 0x8B RWB: 1 SYNC: 0
11101011 10001011 : 0xEB 0x8B RWB: 1 SYNC: 0
11111111 11111111 : 0xFF 0xFF RWB: 1 SYNC: 1
11101011 10001100 : 0xEB 0x8C RWB: 1 SYNC: 0
00000001 01110000 : 0x1 0x70 RWB: 1 SYNC: 0
00000001 01101111 : 0x1 0x6F RWB: 1 SYNC: 0
00000001 01101110 : 0x1 0x6E RWB: 1 SYNC: 0
11111111 11111100 : 0xFF 0xFC RWB: 1 SYNC: 0
11111111 11111101 : 0xFF 0xFD RWB: 1 SYNC: 0
11101010 11101010 : 0xEA 0xEA RWB: 1 SYNC: 1
11101010 11101011 : 0xEA 0xEB RWB: 1 SYNC: 0
11101010 11101011 : 0xEA 0xEB RWB: 1 SYNC: 1
11101010 11101100 : 0xEA 0xEC RWB: 1 SYNC: 0
11101010 11101100 : 0xEA 0xEC RWB: 1 SYNC: 1
11101010 11101101 : 0xEA 0xED RWB: 1 SYNC: 0
11101010 11101101 : 0xEA 0xED RWB: 1 SYNC: 1
11101010 11101110 : 0xEA 0xEE RWB: 1 SYNC: 0
11101010 11101110 : 0xEA 0xEE RWB: 1 SYNC: 1
11101010 11101111 : 0xEA 0xEF RWB: 1 SYNC: 0
11101010 11101111 : 0xEA 0xEF RWB: 1 SYNC: 1