
How to cable to the PR-650

The CMETER routine is written to send signals out the Modem port on the Macintosh to the PhotoResearch P5-650 spectral radiometer.

The modem port takes an 8 pin male plug.  Orient the plug sothat you see three horizontal rows of pins with two pins in the top row, three in the middle row, and three in the bottom row.  The pins are then numbered 1-8 going across each rows and then down through the rows.  (So pin 1 is the upper left, pin 2 the upper right, pin 3 the middle left, etc.)  See Guide to the Macintosh Family Hardware , p. 360 for a picture of the pin-out.

The PR-650 comes with an interface cable that ends in a standard female DB-25 connector.  If you look into the male connector that will plug into the 650 with the long row of pins on top, then the top row is numbered 1-13 from left to right and the bottom row is numbered 14-25.

To get CMETER to work, you need to connect as follows

Mac Pin				DB-25 Pin

1									20
2									4
3									3
4									7
5									2
6									7				(I'm not sure this is necessary)
7									open
8									open

You can buy cables that plug into the modem port on one end and has a DB-25 connector on the other.  What pin is connected to what varies depending on who made the cable.  I suggest you get one, measure its connectivity, and then build a cross-over cable to get the desired overall effect.  (That is what we did.)

The PR-650 cable has a little switch on it with two positions, xfer and ctrll.  The switch should be set to ctrlr.

David Brainard
March 13, 1997
