programming the 67f687

[Mike Klopfer]

I've called the local pioneer distributor and they said that I could get
the 67f687 chip for $38 a piece with a minimum order of $100. They also
said that SSI was making 15/wk. I don't know what this means in terms of
how long it would take to get the chips.

I tried to work out an example of programming th 67f687 for a single pulse
source (e.g. saw blade or gear with teeth ground off). The example is for
a four cylinder engine. The pulse source is a gear with 4N teeth with teeth
0,3,N,N+4,2N,2N+5,3N,3N+6 ground off. I'm assuming that the output of the
tooth sensor is being supplied to the crank input of the 67f687. Also assume
that the gear rotates once every two crank rotations so there are only
2N pulses generated per 360 degrees. These
missing teeth will signal SOP (start of pattern) and EOP (end of pattern).
The location of a pattern is determined by counting the number of teeth 
between two missing teeth.
So CWSP00= 360*4/2N and CWTH00= 2N - 1.
The first pattern is the teeth from 0 to 3 this implies that PRACH1= 0,
PRACL1= 0, PRTN01= 0, PRADD1= 101/2, PATRN1= 2= 3-0-1 (the number of teeth
between the two ground off teeth). Similarly the second 
pattern is the teeth from N to N+4 so PRACH2= (180*4)>>8, PRACL2= (180*4)&0xff,
PRTN02= N,
PRADD1= 101/2, PATRN2= 3= (N+4)-N-1 and so on for patterns 3 and 4 except
PRTN03= 0 and PRTN04= N. 
PAREG1= 0x17 i.e. 1 missing crank pulse as EOP and I'm not sure if it matters
what CRKNUM field is as long as it less than the minimum number of teeth
between a pair of patterns (N-7). Perhaps it should be larger than the maximum
number of teeth in a pattern (5). PAREG4= 0x14 i.e. SOPTYP= missing crank and
EOPTYP= missing crank. PAREG2= 0xc0 i.e. since pattern bit isn't used set it
to 0 and TYP is counted type of pattern so CDEDAT doesn't matter.
PAREG3= 0x60 i.e. PATBT6= not used, CNTCLK= crank pulse is counted to match
patterns. PMREG1= 0x00 i.e resolution of .25 degrees and 1 section of teeth.
PMREG3= 2N i.e. 2N pulses per crank rotation. PMREG5= 360*4/2N ??