Timer processors

Timer processors

An alternative to using a timer/counter is the development of timer computers where a processor is used exclusively to manage and implement complex timing functions over multiple timer channels. The MC68332 is a good example of such a proces-sor. It has a CPU32 processor (MC68020 based) running at 16 MHz and a timer processor unit instead of a communications processor. This has 16 channels which are controlled by a RISC-like processor to perform virtually any timing function. The timing resolution is down to 250 nanoseconds with an external clock source or 500 nanoseconds with an internal one. The timer processor can per-form the common timer algorithms on any of the 16 channels without placing any overhead on the CPU32.

A queued serial channel and 2 kbits of power-down static RAM are also on-chip and for many applications all that is re-quired to complete a working system is an external program EPROM and a clock. The timer processor has several high level functions which can easily be accessed by the main processor by programming a parameter block. For example, the missing tooth calculation for generating ignition timing can be easily performed through a combination of the timer processor and the CPU32 core. A set of parameters is calculated by the CPU32 and loaded into a parameter block which commands the timer processor to perform the algorithm. Again, no interrupt routines or periodic peripheral bit manipulation is needed by the CPU32.