Commodore 64 I/O ROM Expansion Port


Posted on Feb 5, 2014

The output F1 pin 17 of the PLA U17 goes `low` when the BASIC ROM is selected. The KERNAL ROM resides at locations $E000 - $FFFF. The output F2 pin 16 of the PLA U17 goes `low` when the KERNAL ROM is selected. The CHARACTER GENERATOR ROM resides at locations $D000 - $DFFF. The output F3 pin 15 of the P


Commodore 64 I/O ROM Expansion Port
Click here to download the full size of the above Circuit.

LA U17 goes "low" when the Character Generator ROM is selected. The expansion port is an extension of the microprocessor address, data, and control bus. ROML decodes addresses $8000 - $9FFF, and ROMH decodes addresses $E000 - $FFFF. These are outputs from the PLA used to select the catridge inserted in the expansion port. I/O 1 input from U15 decodes addresses $DE00 - $DEFF. I/O 2 output from U15 decodes addresses $DF00 - $DFFF.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

CW Transmitter 5 Watt
Headphone Class-A Power Amplifier
Fm Demodulator Circuit
Strobe Light circuit
usb car charger adapter circuit design
Latching Current Limiter
vu meter schematic
Infra-Red Remote Control Tester
2Y- connection two-speed motor contactor control circuit 2
Constitute a CMOS circuit time adjustment of a spot welder
ISO120 eight-channel isolated and PWS740 0 ~ 20mA current loop circuit diagram



Top