RampDown.v

This module ramps down the field set point in a controlled manner. It is intended for use when a soft trip requires the rf field be ramped down quickly, but not instantaneously. Normally, the set-point data stream passes the module through the in and outports. Following a trigger, however, a snapshot of the interleaved I and Q parts is captured and the I and Q parts are each reduced in magnitude by one unit per predetermined number of clock cycles. These declining components are gated onto the out port and arrive at zero at an interval following the trigger in proportion to their initial values. Later when the module is reset, the in port is again gated onto the out port.

Ports | Parameters | Notes | Example | Illustration

Ports

clk	input	The clock input.
reset	input	Reset input, which clears the ramp registers.
quad	input	Two-bit vector fiducial indicating the current quadrant, for alignment of the I and Q components.
go	input	A vector of triggers.
in	output	The I/Q data stream that ramps to zero the the module is triggered.
out	output	The output data stream that ramps to zero when triggered.
busy	output	Indicates the ramp is in progress.
done	output	A pulse indicates the ramp is completed.
trip	output	Logic level indicating whether the module is tripped. It goes high when `trippulse` pulses. The module is untripped by a reset pulse.
trippulse	output	Pulsed when the ramp down is actually triggered. If the `go[]` trigger vector consists of only one bit, then `trippulse` is pulsed at the same time as `go` pulse. When there is a multi-level trigger, then `trippulse` occurs when all trigger events have occurred simultaneous with the final one.

Parameters

width	16	Data bit width.
duration	32	The inverse slope of the ramp down in clock cycles per decrement of the ramp (at most 256}.
gobits	2	The number of bits of the `go` trigger vector.

Notes

The incoming set point (at the in port) is not changed by a soft trip. Instead, this module blocks the normal set point and replaces it with a ramp to zero. The output of this module remains at zero until it is reset by a global reset, at which point the incoming field set point reasserts itself. Because of this behavior, zero or other nominal values should be written to the incoming set point prior to reset of this module.

Example instantiation in Verilog:

wire	[15:0]		din, dout;
wire	[1:0]		quadrant;
wire			clk, reset, rdBusy, rdDone, Trip;
RampDown
   #(.width(16), .gobits(2), .duration(24))
   rd (
      .clk(clk),
      .reset(reset),
      .en(1'b1),
      .quad(quad),
      .go({Trip, quad==2'b00}),
      .in(ramplocal),
      .out(ramp),
      .busy(rdBusy),
      .done(rdDone)
   );