Odd CIA (Amiga 500)

the odd cia handles the keyboard, parallel port and part of the floppy ready if you have a fault between the cia and the 68k communication, then the kickstart rom will hang at white screen note the even cia is not needed to be present for the system to boot, that controls reading from the floppy drive, expansion port and paula out of reset start by checking the cia is out of reset measure the !reset pin and it should be 5v if not check the u37 7432 or gate that the trace connects to pin 11 output (which feeds also into pin 9 input) the input pin 12 is from the angus/68k/paula reset pine so the cia should come out of reset at the same time as the rest of the system if the or gate is working 68k communication confirm you have good continuity between all of the 68k pins they include the data pins d0 a7, the address pins a8 a11, the e pin and the !write pin the !write pin should toggle during boot slower at first then almost constant once loaded into kickstart the e pin should be a 709 4khz constantly pulse all data and address pins should toggle constantly the address pins toggle slower while initially loading then almost constant once booted paula interrupt the !int2 pin should go high for a second or so, then start pulsing in short pulses low at random intervals once booted it goes to a 10 82hz regular pulse !cs (chip select) this pin sits idle high for about a second while the bios is read, then it starts pulsing randomly during boot once loaded into kickstart it is a constant regular pulse tick (!vsync) the tick pin is the vsync so will show the frequency pulse your monitor output is running at, in this case 49 92hz gary ovl (overlay rom over ram) the gary overlay signal goes high while the bios is loading, and then pulls low afterwards keyboard & joystick the keyboard clock and data pins sit high at 5v dc while booting, if no keyboard is connected the keyboard !led pin is high for a second while the bios loads, then low afterwards so long as the joystick buttons are not pressed the fire0 and fire1 remain at 5v dc parallel port all ppd data pins, and the f (pp acknowledge) pin, and !pc (strobe) pin all sit at 5v dc with nothing connected