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Voltmace Delta 14B Driver

Annotated disassemblies of the driver software for the Voltmace Delta 14B joystick/keypad handset system on the BBC Microcomputer. The Delta 14B/1 interface unit connects up to two handsets (each a 3x4 keypad plus a two-axis analogue joystick) to the BBC Micro's analogue and user ports, multiplexed by a 74LS157. The disc ships two programs — JOYSTIK and KEYPAD — each pairing a 6502 driver with a BBC BASIC front-end held under a rudimentary bit-rotation protection. The original driver software is © 1983 Custom Video Productions; the annotations and disassembly scripts here are © 2026 Acornaeology.

Voltmace Delta 14B Driver glossary

Annotated Disassemblies

Source Listings

The other source that makes up each program: the BBC BASIC front-ends, and the machine-code driver variants held encoded in the image.

• Voltmace Delta 14B/1 KEYPAD loader and resident driver
  • Keypad editor (BBC BASIC front-end) BBC BASIC
• Voltmace Delta 14B/1 JOYSTIK loader
  • Joystick configuration program (BBC BASIC front-end) BBC BASIC

Analyses

• The Voltmace Delta 14B driver system: architecture and runtime

  How the original system fits together: the handset hardware, the two protected programs, the ROL-1 obfuscation and loader, the BASIC front-ends that configure the drivers, and the resident 6502 drivers that hook EVNTV (KEYPAD, a keyboard the MOS polls) and BYTEV (JOYSTIK, an INKEY the MOS asks).

• Reproducing the originals: sources, build and verification

  How the modern build regenerates the KEYPAD/JOYSTIK files byte-for-byte from editable sources (annotated assembly + detokenised BASIC), re-encrypting a greedy-tokenised, ROR-rotated incbin payload and assembling the JOYSTIK driver variants back to bytes; and the whole-file verification that keeps it honest.

• How the KEYPAD editor (BASIC front-end) works

  A line-by-line walkthrough of the KEYPAD keypad-definition editor: reading the configuration DATA tables, the interactive key editor, the matrix scan, and how PROCFIN pokes the resident driver's key table and installs it.

• How the JOYSTIK editor (BASIC front-end) works

  A line-by-line walkthrough of the JOYSTIK configuration/demo program: joystick-configuration choice, the Acornsoft-game presets, defining keys, and how PROCASSEM copies a driver variant to &A00, pokes joystick_map, and patches the chain slot and thresholds.

References

Further reading

• SN74LS157 quad 2-line to 1-line data selector/multiplexer datasheet
  The multiplexer in the Delta 14B/1 interface that strobes the two handsets under software control.