I'm working on an engine management controller from an early 90's car, (Mazda MS-6) which uses an ECU made by Nippon Denso. Most of the technology is easily identifiable due to its age, unlike more modern units.
This unit is based around Motorola chips, including a 6821 pia and a 6840 timer. The cpu is a Motorola special, type SC402617FN and obviously made for Denso as it has their logo on it.
Looking at the firmware shows that its based around a 68HC11 core, but which one? The package is an 84 pin plcc.
I would very much like to at least identify the pinouts and extra on-board functions of the chip so if anyone can assist I would be most grateful.
This is a project I am working on to try and understand how the cpu can keep track of sequential fuel injection at high speeds while attending to all the multitudinous tasks it has to monitor.
Thanks, John Dyer