UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Non-working Commodore PET 3016

SiriusHardware · 26th Feb 2021, 10:17 pm

Mark, are you thinking that PROM _CS is held low for the entire time that the address is within the address range of the PROM? It does look that way - 4 inputs from BA12 to BA15 to the 74154 4-line-to-16 line decoder UD2. No other signal involved in the generation of the chip select. If so this is somewhat reminiscent of the situation with the MK14, you could intentionally damage something by deliberately writing to the PROM address area.

26th Feb 2021, 10:17 pm	#694
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,556	Re: Non-working Commodore PET 3016 Mark, are you thinking that PROM _CS is held low for the entire time that the address is within the address range of the PROM? It does look that way - 4 inputs from BA12 to BA15 to the 74154 4-line-to-16 line decoder UD2. No other signal involved in the generation of the chip select. If so this is somewhat reminiscent of the situation with the MK14, you could intentionally damage something by deliberately writing to the PROM address area. Last edited by SiriusHardware; 26th Feb 2021 at 10:22 pm.