Figure 21 DAFC Assembly Diagram
DAFC Interface to STALO
The DAFC module is used on RVP900 for magnetron systems to interface to a digitally
controlled STALO. The DAFC is driven from the Trig-A trigger output SMA of the IFDR
module.
DC power (+5 VDC) must be provided by running discrete wires.
To supply the STALO power through the ribbon cable between the DAFC and STALO,
connect the +24 VDC pin to a suitable power supply. Otherwise, power the STALO directly.
The DAFC outputs up to 24 TTL lines to the STALO digital control/interface. Since these are
TTL, mount the DAFC within 30 cm of the STALO, if possible.
DAFC Pin Assignments and Jumper Selections
The digital output lines are made available as TTL levels on a 25-pin female "D" connector
(P1). There are 130Ω resistors (R1 through R25) in series, with each output line to help
protect the board against momentary application of non-TTL voltages on its external pins.
However, these resistors do impose a restriction on the input line
configuration of the
receiving device. To assure a valid TTL low level of 0.6 V maximum requires that the STALO
inputs be pulled up to +5 with nothing less than (approximately) 1.2K?. Put another way, the
low level input current of the receiving device should not exceed 4.5 mA. Most STALOs, that
we have seen, use 5 ... 20KΩ pull-up resistors, so this should not be a problem.
All 25 pins of the "D" connector are wired identically on the DAFC board, that is, each pin
connects to one end of a 2-pin jumper (2x25 header H1), the other end of which connects to
a Programmable Logic Device (PLD) chip. The PLD lines can be
configured either as inputs
or outputs, and this single chip handles all of the decoding and driving needs for the entire
board. For each "D" connector pin that is to be used as an AFC output or Fault Status input,
Chapter 4 – RVP Hardware
75
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