Avid Technology Digidesign USD User Manual page 91

Connector Pin Assignments
15
PILOT_IN-
16
PILOT_IN+
17
RET0
18
GPIN0
19
RET1
20
GPIN1
21
RET2
22
GPIN2
23
RET3
24
GPIN3
25
VDD
Shell
GND
USD Serial Cable Pin
Assignments
Mini DIN 8-pin Male to Mini
DIN 8-pin Male
1 2
2 1
3 5
4 4
5 3
6 8
7 7
8 6
Pilot tone input, negative
Pilot tone input, positive
Return from GPI opto-isolator "0"
Input to GPI opto-isolator "0"
Return from GPI opto-isolator "1"
Input to GPI opto-isolator "1"
Return from GPI opto-isolator "2"
Input to GPI opto-isolator "2"
Return from GPI opto-isolator "3"
Input to GPI opto-isolator "3"
+5V DC, fuse protected (see notes below)
Connected to chassis ground
Bi-phase/Tach/GPI/Pilot
Port Interfacing Notes
The six opto-isolators are 6N137 devices.
Each port input passes through a 390 ohm
series resistor to the cathode. Each port re-
turn comes directly from the anode. The bi-
phase/tach inputs share the same return.
The two TTL-level GPI outputs are driven
by a 74FCT541. Each output passes
through a 220 ohm series resistor.
The fuse is thermally activated. The cur-
rent rating varies between 1.0 A at 60˚C
and 1.5 A at 20˚C. The time to trip varies
with temperature and current. The typical
time to trip at 1.5 A is 5 minutes. Time to
trip at 8 A is 5 seconds. After tripping, the
fuse will return to its low-resistance state
when the current is reduced sufficiently.
Appendix C: Wiring Diagrams Pin Assignments 87