HP 8920A - Page 575

575
Chapter 24, Connector, Key, and Knob Descriptions
Connector Descriptions
9. Logic Voltage (data level):
• The voltage on this pin determines the high output voltage and input logic thresh-
olds of the parallel data, strobe, and interrupt pins.
• Either +12 volts or +5 volts is supplied by the radio under test to indicate the HI (1)
logic level it uses for serial/parallel communications. If no signal is supplied, the
logic level defaults to 5 volts.
• The load that this pin presents to an external voltage source depends on how many
lines are pulled low.
• Input range is 5.1 to 20 V dc.
Load at maximum current (all lines pulled low) is 145Ω.
10. No connection
11. Parallel Strobe Out
• This pin outputs a digital pulse to indicate when data is output on the parallel data
pins.
• The leading edge occurs when the pins change state. But, to allow for settling time,
the external device should latch on the level of the pulse or the trailing edge. The
strobe can be set to go high or low with the Strobe Pol field on the RADIO
INTERFACE screen.
• The output level and current sink capability is the same as the parallel data pins.
Strobe pulse width is 5 µs (typical).
Logic Sense is programmable high or low.
12. Interrupt Input 1
• The interrupt lines can be used together or independently. The lines must be armed
for the Test Set to sense an interrupt. This is done in the Interrupt 1 or In-
terrupt 2 fields on the RADIO INTERFACE screen. When an armed interrupt
is pulled low, the Interrupt 1 or Interrupt 2 fields will show that the in-
terrupt is Tripped. The interrupt can only be cleared when the line returns to the
high state and the interrupt is armed again. The status of the interrupt lines can be
read from the RADIO INTERFACE screen or by an HP-IB or IBASIC program. Al-
so, one of the interrupts can be designated as the HP-IB service request (SRQ) in-
dicator.
• Logic is active low.
Input impedance is internally pulled-up to the logic voltage through 100 kΩ.
Logic threshold is the same as the parallel data pins.
13. Interrupt Input 2
• See pin 14.
14. No Connection