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WDC 65C816

WDC 65C816
PDIP40 package
General information
Launched1985 (1985)
Common manufacturer
Performance
Max. CPU clock rate1 MHz to 14 MHz
Data width
  • 8 (external)
  • 16 (internal)
Address width24 bits
Architecture and classification
Instruction set6502
Number of instructions92
Physical specifications
Packages
Products, models, variants
Variant
    • W65C802 (pin-compatible with W65C02)
    • W65C265 (MCU)
History
Predecessors
SuccessorWDC 65C832[1][2][3] (never released)

The W65C816S (also 65C816 or 65816) is a 16-bit microprocessor (MPU) developed and sold by the Western Design Center (WDC). Introduced in 1983,[4] 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 is 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 extends memory addressing to 24 bits, supporting up to 16 megabytes of random-access memory. It has an enhanced instruction set and a 16-bit stack pointer, as well as several new electrical signals for improved system hardware management.

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.

The W65C802 or 65802 is completely software-compatible with the 65C816, but is electrically-compatible with the 6502 and 65C02. Hence the 65C802 could be used as a drop-in replacement in most systems equipped with a 6502 or 65C02. However, the 65C802 cannot emit a 24-bit address, which limits it to a 64 KB address space. The 65C802 is no longer produced.

  1. ^ Mensch, William D. "A Report on the 65c832". Archived from the original on 7 Apr 2024. Retrieved 7 Apr 2024.
  2. ^ "W65C832 Information, Specification, and Data Sheet (March 1990)" (PDF). ReActive Micro. 6 Sep 2010 [Mar 1990]. Archived (PDF) from the original on 7 Apr 2024. Retrieved 7 Apr 2024.
  3. ^ "W65C832 Information, Specification, and Data Sheet" (PDF). 6502.org. Archived from the original (PDF) on 30 Jun 2023. Retrieved 7 Apr 2024.
  4. ^ Chronology of Microprocessors (1980–1989)

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