What does 65802 stand for? 

65802

The W65C816S (also 65C816 or 65816) is an 8/16-bit microprocessor (MPU) developed and sold by the Western Design Center (WDC). Introduced in 1985, the W65C816S is an enhanced version of the WDC 65C02 8-bit MPU, itself a CMOS enhancement of the venerable MOS Technology 6502 NMOS MPU. The 65C816 was the CPU for the Apple IIGS and, in modified form, the Super Nintendo Entertainment System. The 65 in the part's designation comes from its 65C02 compatibility mode, and the 816 signifies that the MPU has selectable 8- and 16-bit register sizes. In addition to the availability of 16-bit registers, the W65C816S features extended memory addressing to 24 bits, supporting up to 16 megabytes of random-access memory, an enhanced instruction set, and a 16 bit stack pointer, as well as several new electrical signals for improved system hardware management. While the 65816 features 24-bit addressing, it isn't a true 24-bit computer. Programs still operate in 64K chunks since registers are 16 bit. To access other parts of internal memory a technique similar to bank switching is needed. Apple, Atari and Commodore all opted for the Motorola 68000 processor alternative that offered a fully 32-bit programming model when it came to replacing their 6502-based lines of 8-bit computers, despite the 65816 being faster cycle for cycle.At reset, the W65C816S starts in "emulation mode", meaning it substantially behaves as a 65C02. Thereafter, the W65C816S may be switched to "native mode" with a two instruction sequence, causing it to enable all enhanced features, yet still maintain a substantial degree of backward compatibility with most 65C02 software. However, unlike the PDIP40 version of the 65C02, which is a pin-compatible replacement for its NMOS ancestor, the PDIP40 W65C816S is not pin-compatible with any other 6502 family MPU. Related to the W65C816S is the W65C802, which had the same internal structure and 16-bit support, but used a 40-pin layout compatible with the original 6502. This allowed it to be used as a drop-in replacement in certain roles. However, the 65C802 could not emit a full 24-bit address, which limited it to 64 KB of memory. The 65C802 and its relatives are no longer produced.

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