Subject	Re: CAS Signal
Posted by	Cjw3 on October 12, 2012 at 10:22 PM
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In Reply To	CAS Signal posted by daygobaker on October 12, 2012 at 08:53 PM
Message	SOMEWHERE on this Forum is a Break-Apart picture of the CAS.. it's VERY good work, and makes it clear as to how it sends Sigs to the ECU.. If you can, hunt it down.. The ECU will send power to the CAS.. it will use this to power up it's internal Goodies.. The Crank Sig is 360 pulses per crank rev. one per each degree. That should be 720 Pulses per Cam Rev.. I've not Checked it.. but my reading says it should be.. The Cam Sig is 6 Pulses per Rev of the CAM.. Each 'Cylinder Pulse' ( Starting with Cylinder ONE ) is longer than the Next one.. Cylinder ONE Pulse lasts about 5 Crank Pulses.. Cylinder TWO lasts about 10 Crank Pulses.. ( Pulses Approximated for Clarity ) and so on till Cylinder 6 lasts 30 Crank Pulses.. I do not know what the Exact Pulse Count is for Cyl 1, but the Idea is there.. each one gets a longer count.. When the CAS-CPU ( It's in the ECU Housing ) sees a CAM Sig line Trigger, it will then Count the Number of CRANK Sig Pulses the CAM Sig is Down ( Triggered ), and that will tell the CAS-CPU which CAM Cylinder Sig has just Passed.. In the ECU Housing are Four CPU looking Chips.. one is the CPU for the Engine Fuel and Spark, and it runs the 'PROM' Program that everybody Changes.. another of the CPU Looking Chips is the CAS-CPU.. it keeps track of the CAS Signal, and passes the Information over to the Main CPU as it's requested. I think One other Big Chip is the Analog to Digital Converter, and the Last One is the Signal Timer that will take the Main CPU Injector and Ignition Timing, and make sure it happens when it's needed, and timed by the Information of the CAS-CPU.. From my Reading, that is the Basics of what is happening inside the ECU Case.. OLD School ECU Programming (OBD0 Type with Limited CPU Capacity ) used a Crank Sig and Only ONE Cam Sig Trigger.. the Engine needed TWO Full Starting Revolutions to figure out which Cylinder is going to Fire.. this resulted in LONG Start Cranking Times on the Early ECU Type of Cars.. Not all Early ECU Types used this Method, and many Tricks were used to make the Cars start Faster.. Cj
Follow Ups	CAS Signal - daygobaker 20:53:01 10/12/12 Re: CAS Signal - Cjw3 22:22:13 10/12/12 Its an optical rotary encoder that sends a square wave - Supermario680 (WI) 19:05:04 10/13/12 Re: CAS Signal - daygobaker 21:35:40 10/14/12 Re: Re: CAS Signal - Cjw3 13:11:16 10/15/12
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