I was doing some debugging with our other products that use the 7842 & noticed that on a particular VGA resolution(1920x1200@60hz), the measured vtotal was not the same.
In this case the vtotal measured were as follows:
product 1(7842) 1235*
product 2(7842) 1245
(Current project)7850 1242
* correct/expected value
These values come from the cp map(LCF in 7850, SCF in 7842). On product 2, its off enough such that its mis-detected as 1600x1200
I was not expecting these values to be that far off from product to product.
So couple questions:
- Can you tell me what would cause these values to vary from product to product?
- could this be reasonable or expected based on part tolerances, pcb layout, etc?