Software

SOFTWARE ARCHITECTURE
The 68HC16Z2 microcontroller is the main computing unit of the Powertrain Control Module (PCM). The 68HC11D3 and K4 microcontrollers control fuel and spark respectively. They handle the critical timing requirements of their tasks, communicating with the Z2 using high level commands.

The Z2 operating system is the heart of the software and was written expressly for this PCM. Every 500 microseconds the Z2 interrupts what it is doing to perform periodic tasks such as updating sensor inputs values and checking for the occurrence of a crank position pulse. If this pulse is observed, a program known as the decision maker is executed and performs high priority tasks such as fuel and spark calculations, and RPM processing. Low priority tasks (i.e. OBDII processing, SCI and CCD communications) are executed during the time between crank pulses.

The Z2 software is divided into a main operating strategy and three separate calibration areas. The main strategy contains information specific to the various engines and transmissions supported by this PCM. Once installed, the information contained in this area is fixed for a given engine and transmission. Changes to this data, if required, can be performed only by computer programming personnel. The calibration areas (engine, transmission and OBDII) contain information relating to emissions, fuel economy and driveability and can be altered directly by calibration personnel.