VTX5000: Part 3 - Software ROM
Read OriginalThis article is the third part of a series on the VTX5000, a vintage viewdata terminal for the ZX Spectrum. It explores the 8KB software ROM, detailing its memory map including a jump table, embedded BASIC program, Z80 machine code, character font, splash screen, and configuration data. The focus is on memory paging techniques using the Spectrum's ROMCS line and trampoline routines copied to RAM to safely switch between the Spectrum and VTX ROMs during interrupts. It covers the technical implementation of ROM switching with the Intel 8251 UART and provides code examples of the trampoline functions.
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