[MacDV] DV - FW pinouts

[Peter Tattersall]

On Friday, May 23, 2003, at 10:01  AM, Frank Farwell wrote:

> Can anyone tell me how the 4 pins on the FW cable are used? do 2 
> supply DV video and then the other 2 iMovie uses to control the 
> camcorder?
>
> trying to pin down a problem here.
>
> frank farwell

Google is helpful here - it gets you to a number of sites with pinouts 
for both the 4-pin and 6-pin connectors. Try 
http://www.asusemag.com.tw/tech/ch2/ch2-1.htm for details, but for your 
question....

No, there are two serial lines with information going in one direction 
on each line, and control information and video information share the 
lines.

1 - TPB-
2 - TPB+
3 - TPA-
4 - TPA+

TP = Twisted Pair, so there are two twisted pairs in the cable (in the 
6-pin versions, power and ground lines are added). The B pair carries 
data on transmit, the A pair carries data on receive. While the data is 
sent on one pair the other pair is strobing to validate the data, so 
both pairs need to be intact to reliably exchange information. If for 
some reason the strobe signal wasn't sent on one line you would have a 
situation where, say, the camera could send video info and control info 
to the computer but the computer could not send video and control info 
back to the camera. The cables would be intact, the problem would be in 
the camera or the computer. If the cable itself has a problem, nothing 
would work in either direction.