AD8108 Analog Devices, AD8108 Datasheet - Page 26

• Manufacturer Part Number: AD8108
• Description: 325 Mhz, 8x8 Buffered Video Crosspoint Switch (Gain=1)
• Manufacturer: Analog Devices

AD8108/AD8109
When you launch the crosspoint control software, you will be
asked to select the printer port you are using. Most modern PCs
have only one printer port, usually called LPT1. However, some
laptop computers use the PRN port.
Figure 18 shows the main screen of the control software in its
initial reset state (all outputs off). Using the mouse, any input
can be connected with one or more outputs by simply clicking
on the appropriate radio buttons in the 8 × 8 on-screen array.
Each time a button is clicked on, the software automatically
sends and latches the required 32-bit data stream to the evaluation
board. An output can be turned off by clicking the appropriate
button in the Off column. To turn off all outputs, click on RESET.
The software offers volatile and nonvolatile storage of configura-
tions. For volatile storage, up to two configurations can be
stored and recalled using the Memory 1 and Memory 2 Buffers.
These function in an identical fashion to the memory on a
pocket calculator. For nonvolatile storage of a configuration, the
Save Setup and Load Setup functions can be used. This stores
the configuration as a data file on disk.
Overshoot on PC Printer Ports’ Data Lines
The data lines on some printer ports have excessive overshoot.
Overshoot on the pin that is used as the serial clock (Pin 6 on
the D-Sub-25 connector) can cause communication problems.
This overshoot can be eliminated by connecting a capacitor
from the CLK line on the evaluation board to ground. A pad
has been provided on the solder-side of the evaluation board to
allow this capacitor to be soldered into place. Depending upon
the overshoot from the printer port, this capacitor may need to
be as large as 0.01 µF.