H8300

H8 is the name of a large family of 8-bit, 16-bit and 32-bit microcontrollers made by Renesas Technology, originating in the early 1990s within Hitachi Semiconductor and still actively evolving as of 2006. The family of largely CISC machines is unrelated to the higher-performance SuperH family of 32-bit RISC-like microcontrollers.

It is supported in the Linux kernel since version 4.2.

Subfamilies include the 8/16-bit H8/300 and H8/500, the 16/32-bit H8/300H and H8S and the 32-bit H8SX series, each with dozens of different variants, varying by speed, selection of built-in peripherals such as timers and serial ports, and amounts of ROM, flash memory and RAM. Built-in ROM and flash memory tends to range from 16 KB to 1024 KB, and RAM from 512 B to 512 KB.

The basic architecture of the H8 is patterned after the DEC PDP-11, with eight 16-bit registers (the H8/300H and H8S have an additional bank of eight 16-bit registers), and a variety of addressing modes.

Both H8/300H and H8S have eight 32-bit registers, each of which can be treated as one 32-bit register, two 16-bit registers, or two 8-bit registers, with the H8S having an internal 32-bit configuration. Several companies provide compilers for the H8 family, and there is a complete GCC port, including a simulator. There are also various hardware emulators available.

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