![]() Moving the card to another (modern) machine to exchange files with my PCjr must be possible.I want to run stuff on the card, so its contents must be accessible as if it were a floppy or hard drive.Regulator, level converter and microsd slot. For the card slot, I used a small Adafruit PCB which came with its own To access theĬartridge signals, I soldered wires between one of my cartridge PCBsĪnd the DIP components on the breadboad. Schematic, page 2 - Shift Registers, card interface (voltage regulator and level converters)īefore making a PCB, I tested everything on a breadboard, but not entirely without soldering. Schematic, page 1 - PCjr Cartridge, address decoding and ROM The optional ROM is accessible from D0000 to D5FFF (24 kB).To/from the shift registers and the card. Reading from anywhere in the D6100-D61FF range generates a clock pulse which causes one bit to be shifted.The read returns the last byte received by the other shift Loaded corresponds to address bits A0-A7. Reading from D6000-D60FF loads the 74ls165 shift register with next byte to be transmitted.The cartridge uses the CS2 signal from the slot and is therefore visible from D0000 to D7FFF. ![]() ![]() Since the cards communicate serially (SPI), I used a pair of shift registers (one for transmitting to the card andĪnother for receiving) to perform parallel/serial conversion in the hope of getting better performance by (Select/Deselect the card, load a value to transmit, etc). This does not mean the cartridge slot cannot send information, since the address being read is in itself outgoingĭata! So I divided the cartridge memory space and arranged so that reading from certain address ranges would have Quite a few signals from the PCjr BUS are available on the cartridge slot, but there is no write signal. ![]()
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