Questions:  A) Are both channels terminated in a 100 ohm series impedance?
B) A 74ALS244 is specified for Channels 4,5,6,7.  What is the driver for Channels 0,1,2,3?

 

Answers:  The DT340 is a very high speed I/O Counter Timer Board.  In order to meet the FCC and ce EMI requirements on the clocks we had to properly
terminate the output signals.  Channels 0-3 have a C244 driver with a series 150 ohm resistor. On the output side there is a 301 ohm resistor to ground. This works out to be a 100 ohm output impedance.  Channels 4-7 are the same except the series resistor is 100 ohms for an output impedance of 75 ohms.  *Dated 07/24/01.