IEC support for Corsham's xXIM and Microsoft Basic

I’ve been extending Dave McMurtrie’s implementation of IEC disk support for the KIM-1 (from the ca65 port of Nils Andres, aka netzherpes). I’ve added long file names, sending arbitrary commands to the disk, directory listing, verify and add a jump-table based interface, and used that to add disk support to Corsham’s xKIM monitor and Microsoft’s KB9. Here is a video of it working:

Code at my GitHub repository:

• xkim1541: https://github.com/eduardocasino/xkim1541
• xKIM with IEC support: https://github.com/eduardocasino/xKIM/tree/IEC_support
• KB9 with disk support: https://github.com/eduardocasino/msbasic/tree/IEC_support

Build

This is still experimental, use at your own risk!

Requirements

• Expanded KIM-1 (or PAL-1) with RAM from 2000 to DFFF, ROM from E000 to FFFF and the IEC circuit based on Dave’s design, like the one in Ralf’s expansion or my own buffered motherboard.
• Linux, WSL or any unix-like system with git, bash, gmake and Python.
• Clone the xkim1541 repository and build using make. You’ll need to have Python installed as there is a script that generates the include file depending on the base address. By default, the code is generated to be loaded at 0xF000. You can change it editing the OFFSET variable in the Makefile. I do not recommend modifying the other two variables: ZPINIT and BSSINIT, as they have been chosen to not interfere with either xKIM or KB9.

Clone the xXIM repository and switch to the IEC_support branch. Copy the iecproto.inc file generated in the previous step. Build using make IEC_SUPPORT=1. Burn the xKIM-0.bin file to a ROM at offset 0xE000

Clone the KB9 repository and switch to the IEC_support branch. Build with make. By default, it is assumed that xkim1541 starts at 0xF000. Modify the defines_kimiec.s file if you put it anywhere else. Binary and hex files are generated in the tmp directory, with offset 0x2000. You can build it at a different one editing the PAGE variable in the makefile. For example, I built mine at PAGE = 40 (0x4000) because I’ve got a Visual Memory Card at 0x2000. You can build a prg file with make prg, so you can add it to a disk image.

Usage

Jump to xKIM at addr 0xE000. There are some modified or new commands:

C ........... Send a command to the drive
D ........... Disk directory
R ........... Read PRG file from disk
V ........... Verify PRG file on disk
W xxxx xxxx . Write memory to PRG file

I f you are familiar with xKIM, they are self-explanatory. If not, see the video. When writing to disk, end address must actually be address of last byte + 1

If you can generate a physical or pi1541 or similar image, make one with kb9v2.prg and load using the R command. You’ll see the address where the program is loaded to. Just jump (J) to that address to start MS Basic.

New and modified BASIC tokens:

• LOAD and SAVE , without arguments, work the same as the originals: loads and saves the current program from/to tape.
• LOAD "<FILE>" and SAVE "<FILE>" will load and save file <FILE> from/to disk.
• VERIFY "<FILE>" will compare the current program in memory against the <FILE> program on disk.
• DIR will list disk directory contents to screen. The current program in memory is not changed.
• DCMD "<CMD>" will send command <CMD> to disk. Example: DCMD "S0:X*" will delete (scratch) all files beginning with “X”.