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Modular 6502 SBC with emulated CPU
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Modular 6502 SBC with emulated CPU The minimum system consists of an ATMega32, an SRAM IC and some components to provide a clock source and an RS232 interface. A serial EEPROM can be added as non volatile program storage. Examples in the source code showcase, how parallel IO can be added from simple latches to 65xx IO ICs. If you need a version for the ATMega16 go to the "low-flash" branch. The master branch now includes the optional IO subprocessor and the optional MMU with 512k RAM. The emulation provides: some of the ATMega's internal IO capabilities RS232 I²C/TWI SPI Timers Interrupt pins as IRQ and NMI inputs proper sequencing of tags for parallel IO devices glue logic replaced by emulation IO modules and simple registers a debugger & monitor outside of the emulated CPUs code space alter and display registers and memory program control – start, stop, single step & breakpoint trap undefined opcodes or STP instruction loading or booting code images to RAM from RS232 (monitor console) serial I²C or SPI EEPROM The achievable 6502 equivalent clock speed is approximately 2 MHz at 16 MHz ATMega clock. In order to combine the required IO blocks for your own SBC design, some AVR assembler knowledge is required. The emulator source code contains extensive comments about configurable items and the usage of emulated registers in the IO page.