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Chapter 6 Advanced Topics 61
Connector hardware and cables of many different types are widely available and can
often be obtained locally, such as at a nearby Radio Shack
®
store. A list of possibly
useful items follows. Note that, although the items listed may be appropriate in many
situations, they might not meet your specific needs.
25-pin female type D-subminiature solder type connector (Radio Shack
®
part no
276-1548B).
RG/58U coaxial cable.
Shielded Metalized hood (Radio Shack part no 276-1536A).
BNC connector(s) type UG-88 Male BNC connector (Radio Shack part no 278-103).
Example
Suppose you needed to build a cable to monitor the line TTL OUT 1. One approach
would be to build a cable assembly as described in the following paragraphs. This
procedure could easily be adapted to other situations.
1. Begin with a 25-pin female type D-subminiature solder type connector (Radio Shack
part no 276-1548B). This connector has 25 solder points open on the back.
2. Referring to Table 5, note that pin 8 = GND and pin 9 = TTL OUT 1.
3. Using coaxial cable type RG/58U (6 feet length), strip out the end and solder the
outer sheath to pin 8 (GND) and the inner line to pin 9 (TTL OUT 1). Then apply
shielding to the lines to insulate them.
4. Mount the connector in a Shielded Metalized hood (Radio Shack part no
276-1536A).
5. Build up the cable (you can use electrical tape) to where the strain relief clamp
holds.
6. Connect a BNC connector (UG-88 Male BNC connector) to the free end of the cable
following the instructions supplied by Radio Shack on the box (Radio Shack part no
278-103).
7. To use this cable, connect the DB-25 to the TTL In/Out connector on the back of the
ST-133.
8. To check the cable, start WinView/32 and open the TTL Diagnostics screen (located
in WinView under Hardware Setup - Diagnostics). Click the Write radio button.
Then click the Output Line 1 box. Next click the OK button to actually set TTL
OUT 1 high. Once you set the voltage, it stays until you send a new command.
9. Measure the voltage at the BNC connector with a standard voltmeter (red on the
central pin, black on the surrounding shielding). Before clicking OK at the TTL
Diagnostics screen you should read 0 V. After clicking OK you should read +5 V.
Note that adding a second length of coaxial cable and another BNC connector would be
straightforward. However, as you increase the number of lines to be monitored, it
becomes more convenient to consider using a multiple conductor shielded cable rather
than individual coaxial cables.