Ricoh 5A22

Ricoh 5A22 is a microprocessor which was manufactured by Ricoh for the game console Super Nintendo Entertainment System ( SNES) and it serves as the main processor. The 5A22 is based on the 65C816 from WDC ( which, for example, use the Apple IIgs found ). The processors listed are taken from the processor family of the MOS the 6502.

Main features

In addition to the 65C816 core of the 5A22 has the following additional components:

• Interface lines for the controller port for both serial and parallel access to the controller data
• An 8- bit Parallel-I/O-Port, which remained largely unused in the SNES
• A circuit for generating interrupt NMI ( non-maskable interrupt ) is within the vertical blanking interval
• A circuit for generating IRQ interrupts to a calculated image position
• A DMA unit which supports two primary modes: Normal DMA for block transfers at a data rate of 2.68 MB / s
• DMA within the horizontal blanking interval, the transfer of small amounts of data at the end of each scan line, outside of the active display time

Performance

The CPU uses a system with variable speed, the access speed is determined by the requested location. The bus having a clock rate of 3.58 MHz for non- access cycles and when accessing the bus B or most of the internal register, and either 2.68 or 3.58 MHz, when the bus A is accessed. The controller ports of the serial registers operate only at 1.79 MHz. The 5A22 works with about 1.5 MIPS and has a theoretical peak of 1.79 million 16 -bit additions per second.