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The methods by which the MPU state is preserved and restored within an ISR will vary with the different versions of the 65xx family. For NMOS processors (e.g., 6502, 6510, 8502, etc.), there can be only one method by which the accumulator and index registers are preserved, as only the accumulator can be pushed to and pulled from the stack. [5]
Such was the case in the 6502, which used the first memory page, or "zero page", to provide faster access, and the second page, "page one", to hold a 256-byte stack. By the 1980s, these assumptions were no longer valid; many machines based on these processors now shipped with the maximum 64 kB that the 6502 could address, using the far less ...
Merlin is a MOS Technology 6502 macro assembler developed by mathematics professor Glen Bredon for the Apple II under DOS 3.3. It was published commercially by Southwestern Data Systems, [1] later known as Roger Wagner Publishing. Merlin continued to be updated as successors to the 6502 became available: first the 65C02 and later the 65816 and ...
The 6502 programming manual thus requires each ISR to reset or set the D flag if it uses the ADC or SBC instruction, but occasionally a human programmer may mistakenly omit to do this, causing a bug. For example, the Commodore 64 's KERNAL did not correctly handle this processor characteristic, requiring that IRQs be disabled or re-vectored ...
ece.gatech.edu The School of Electrical and Computer Engineering (ECE) at the Georgia Institute of Technology , is an academic institution specializing in electrical and computer engineering education, research, and innovation.
Their moves legitimized the 6502, and by the show's end, the wooden barrel full of samples was empty. [citation needed] The 6502 would quickly go on to be one of the most popular chips of its day. A number of companies licensed the 650x line from MOS, including Rockwell International, GTE, Synertek, and Western Design Center (WDC).
The Commodore PET is a line of personal computers produced starting in 1977 by Commodore International. [3] A single all-in-one case combines a MOS Technology 6502 microprocessor, Commodore BASIC in read-only memory, keyboard, monochrome monitor, and, in early models, a cassette deck.
The 6507 uses a 28-pin configuration, with 13 address pins (A0..A12) and 8 data pins (D0..D7). The seven remaining pins are used for power (Vss, Vcc), the CPU timing clock (φ0, φ2), to reset the CPU (the /RES pin), to request a CPU wait state during its next memory read access (the RDY pin), and for the CPU to indicate if a read or write memory (or MMIO device) access is being performed (the ...