mjmahon

Note that any keyboard adapter will allow "users" to interfere with each other's "keystrokes". Each axis of a digital joystick has three permitted states, usually requiring two bits. Each button is another bit. Therefore, four single-axis joysticks with one button each require 12 independent bits (since they can all be operated asynchronously). An analog joystick joystick input can only be read reliably to within 1% or so--allowing a maximum of 6 independent bits to be read. (And, since any switch can be operated at any time, a sample-and-hold would be needed to guarantee no false reads as a result of a switch changing state in the middle of a read.) So analog sensing is out unless the inputs won't change during the read, and can reliably provide only about 6 independent bits of input per read. If you really need a lot of parallel inputs, use a general-purpose parallel port card with an external joystick adapter.

That will get you 256 bytes of the EPROM. The rest of it is bank-switched into the $C800..$CFFF space when the slot is accessed. A short machine language program can: 1) deselect any switched-in I/O expansion ROM by accessing $CFFF, then 2) selecting the desired slot by referencing something in the $Csxx space, then 3) copying $C800..$CFFF to a spot in RAM (like $4000). Make sure that you don't reference $CFFF until the last byte, or the ROM will be deselected. In fact, the byte read from $CFFF may be invalid! Each designer took a different approach to using I/O expansion space, so expect to spend some disassembly time figuring out how it's used. Some I/O EPROMS are larger than 2K, and use a further bank-switching scheme implemented on the card. Some cards (e.g.: Vulcan) also involved SRAM in the bank switching to provide on-board buffering.

The //e, IIc, and IIgs do have key rollover and "any key down" sensing, so if multiple keys are pressed and held, it's possible to tell when they were pressed and when the last one was released.

No worries--the "standard" cable was whatever Apple bought 50,000 of that month. In other words, it varied in color, length, and connector molding. Just pick one you like. Any good RCA video cable is perfect.

Merlin does indeed use a modified text file format, but it can easily import standard text files. After loading the text file, use the FIX command to convert it to Merlin's format. And remember that each space is a tab.