English Amiga Board - View Single Post - Amiga 600 schematics nearly put into Kicad

Stedy · 03 January 2021, 12:24

Hi,

I checked _KBRESET, it stays low for 600ms after application of power, then goes high, this is expected operation. The _HLT signal is at logic 1, expected as it only has a pull-up resistor.

I did get _RST to go to logic 1, by changing the resistor value from 4K7 to 1K. I removed the pull-up resistor, inserted my DMM, set to measure current, and observed the current flowing. There is most likely still a problem somewhere else.

I can see that _AS is low, indicating the start of a cycle and _DTACK is high, this tells me a bus cycle started but did not complete. I need to check a few more signals around the MC68000 and GAYLE.

I have documents on AGNUS, DENISE, GAYLE & the CIA chips, this helps me understand how things are meant to work, just reading some of them now.

03 January 2021, 12:24	#403
Stedy Registered User Join Date: Jan 2008 Location: United Kingdom Age: 46 Posts: 733	Hi, I checked _KBRESET, it stays low for 600ms after application of power, then goes high, this is expected operation. The _HLT signal is at logic 1, expected as it only has a pull-up resistor. I did get _RST to go to logic 1, by changing the resistor value from 4K7 to 1K. I removed the pull-up resistor, inserted my DMM, set to measure current, and observed the current flowing. There is most likely still a problem somewhere else. I can see that _AS is low, indicating the start of a cycle and _DTACK is high, this tells me a bus cycle started but did not complete. I need to check a few more signals around the MC68000 and GAYLE. I have documents on AGNUS, DENISE, GAYLE & the CIA chips, this helps me understand how things are meant to work, just reading some of them now.