Installation Instructions

Hardware Installation
RVP8 User’s Manual
September 2005
2–32
The DAFC board runs off of a single +5V power supply which can be applied either from the
STALO through the “D” connector, or externally through the terminal block. There are also
provisions for supplying +24V (approx.) between the terminal block and the “D” connector,
which is handy for cabling power to a STALO that requires the second voltage. Two green
LEDs indicate the presence of +5V and +24V. Terminal block Pin #1 is +5V, Pin #2 is +24V,
and Pin#3 is Ground. Pin #1 is the one nearest the corner of the board.
There is an option for having a “Fault Status” input on the “D” connector of the DAFC. Since
the board is completely passive in its connection to the uplink, the fault status bit will not affect
the uplink in any way. Rather, the bit is simply received by the board (with optional polarity
reversal) and driven onto the terminal block (P3) from whence it can be wired to some other
device, e.g., a BITE input line of an RCP02. A yellow LED is included to indicate the presence
of any external fault conditions.
The “AB” position of the 3-pin “Alarm” jumper (H9) connects the Fault Status signal to Pin #4
of the terminal block, whereas the “BC” position grounds that terminal block pin. A second
ground can be made available at Pin #5 of the terminal block by installing a jumper in the “BC”
position of the “Spare” 3-pin jumper (H10). This second ground could be used as a ground
return when the Fault Status line is driven off of the terminal block. The “AB” position of the
“Spare” jumper is reserved for some future input or output line on the terminal block.
Both the shield and the center conductor of the uplink SMA input connector (P2) are electrically
isolated (> 100KW) from the rest of the DAFC board. Moreover, the SMA connector pins
themselves are high-impedance and unterminated. What this means is that the board can be teed
into the uplink cable anywhere in the cable run from the RVP8/Rx board to the IFD. Since the
cable is driven by the RVP8/Rx, it must be at one end of the cable; and since termination is
provided by the IFD, it must be at the other end. The DAFC can be anywhere in the middle. Be
sure, however, that the TEE is located right at the DAFC itself so that an unterminated cable stub
is not created. A red LED is included to indicate that a valid uplink data stream is being
received.
A crystal oscillator is used to supply the operating clock for the on-board logic, and there are
two choices of frequency to use. If jumper H2 is “Off” then the crystal frequency should be
equal to the IFD’s sampling clock f
aq
, and if H2 is “On” the frequency should be (0.75 f
aq
).
Additional information about using AFC can be found in Sections 2.2.11, 3.2.6, and 5.1.3.
2.4.1 Example Hookup to a CTI “MVSR-xxx” STALO
Here is a complete example of what would need to be done in hardware and software to interface
the DAFC to a Communication Techniques Inc. digital STALO. The electrical interface for the
STALO is via a 26-pin ribbon cable which carries both Control and Status, as well as DC power.
This cable can be crimped onto a mass-terminated 25-pin “D” connector (with one wire
removed) and plugged directly into the DAFC. The resulting pinout is shown in Table 2–11.
The STALO frequency is controlled by a 14-bit binary integer whose LSB has a weight of 100
KiloHertz. In addition, the “Inhb” pin must be low for the STALO to function. Power is
supplied on the +5V and +24V pins, and two grounds are provided. An “alarm” output is also
available.