xdev

Cross-development firmware for the Foenix F256Jr and F256K, used with FoenixMgr. It runs before the next firmware program and checks for a request in RAM:

• CROSSDEV: launch a PGX or PGZ program uploaded by FoenixMgr.
• COPYFILE: verify a file uploaded to RAM and write it to the SD card (drive 0).
• No request: continue booting with kernel firmware block $42.

Build

Requires 64tass and GNU Make 4.3 or newer. From this directory:

make          # build xdev.bin and the assembly listing xdev.lst
make clean    # remove generated output

The build selects the 65C02 CPU, enables case-sensitive symbols, and treats assembler warnings as errors. Override TASS to select another 64tass executable or TASSFLAGS to change the assembler flags. No Windows tools are needed.

The source uses native 64tass syntax; it is no longer Merlin32 source. The port replaces Merlin directives, local labels, bank-byte extraction, and table loops. The generated image is exactly 8 KiB, with a kernel module header and a load address of $A000. Assembly fails if the module exceeds that block.

Firmware integration

xdev occupies flash sector $01 (one 8 KiB block, kernel firmware block $41) and hands normal boot to kernel block $42. update.csv contains 01,xdev.bin for the firmware updater, matching this layout.

make flash    # build and program only flash sector 01 using FoenixMgr

The flash target defaults to --target f256k and stages the image in RAM at $380000, matching pexec's flash workflow. Override TARGET, FLASH_ADDRESS, or FOENIXMGR as needed, for example make flash FOENIXMGR='foenixmgr --port /dev/ttyUSB0'. Plain make only builds.

FoenixMgr places an eight-byte request signature at zero-page address $80. For CROSSDEV, the entry address is at $88. xdev clears the signature and restores physical block 5 in CPU slot 5 before jumping to the program.

For COPYFILE, the transfer at physical address $010000 contains a NUL-terminated filename, a four-byte little-endian CRC32, a three-byte little-endian file length, then the file data. The maximum length is $06FC00 (447 KiB). The CRC uses polynomial $EDB88320, an initial value of zero, and no final XOR. PCopy waits for reset after completion or an error.

Source layout

• xdev.s: module header, request detection, and program launch.
• pcopy.s: transfer validation and SD-card copying.
• mmu.s: banked-memory access and mapping restoration.
• file.s: wrappers for asynchronous kernel file operations.
• crc32.s: transfer checksum calculation.
• term.s: text output and number formatting.
• kernel_api.s: kernel entry points and argument definitions.