Hitachi 6309
HD63C09EP
Developer	Motorola, Hitachi
Manufacturer	Hitachi
Type	Microprocessors
Introduction	1982 (launch)
Architecture	8-bit with support for 16/32 arithmetic
ISA	6309
Word size	8 bit 1 octets 2 nibbles
Technology	CMOS
Clock	1 MHz-5 MHz
Package	DIP40, CG40, CP44, FP52, FP54

The 6309 was a family of 8-bit CMOS microprocessors designed by Hitachi and released in late 1982. The 6309 was advertised and marketed as a licensed low-power CMOS version of the Motorola 6809. This chip was also compatible with rest of the components in Hitachi's HMCS-6800 family.

Renewed interest in the 6309 was brought about during the late 1980s (Japan) and 1992 (US/Europe) when a number of previously unknown and undocumented features surfaced. Some of those features were quite considerable for the time - including hardware support for 32-bit arithmetic, block transfer, bit manipulation, and faster operations.

History

Hitachi released the 6309 in late 1982 as a licensed second source for the 6809. The 6309 was advertised and sold as 100% compatible CMOS version of 6809. Being more power efficient and cooler, the 6309 became quite popular in the CoCo community as a replacement in their systems. Various observable differences in the two microprocessors were spotted very early on - particularly in the way illegal instructions were being handled. Those reports were simply seen as possible bugs in the Hitachi version.

One of the earliest publications explaining some of the differences in the 6309 came from the Japanese Personal Computer Magazine "Oh!FM" published by SoftBank. In their April 1988 issue, it was revealed that the 6309 actually run in emulation mode by default and could in fact be switched to run in native mode which had a large set of extended features including additional registers, 32-bit quad-word arithmetic, and a number of trap modes. It wasn't until 4 years later in 1992 when Hirotsugu Kakugawa, a computer engineering graduate student from Japan, posted a memo named "A MEMO ON THE SECRET FEATURES OF 6309" to comp.sys.m6809 exposing those features in English from the Oh!FM magazine.

possible reasons

There has been a number of speculations as to why Hitachi never documented those features. In fact, even to date, Hitachi has never officially confirmed their existence. Hitachi has been known to make minor tweaks and adjustments to products they license whenever they see fit. It has been speculated that their contract with Motorola simply restricted them from doing the same with the 6809. It's entirely possible Hitachi chosen to not document those features to steer clear of legal issues.

Members

Part	Clock	OP Temp	Packages	Notes
HD63B09	2 MHz	-20 °C - 75 °C	HD63B09P - DIP40
HD63B09E	2 MHz (Ext.)	-20 °C - 75 °C	HD63B09EP - DIP40	External clock
HD63C09	3 MHz	-20 °C - 75 °C	HD63C09P - DIP40
HD63C09E	3 MHz (Ext.)	-20 °C - 75 °C	HD63C09EP - DIP40	External clock

Design

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ISA

Main article: ISA

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See also

• 6809