Barracuda RV8 Manual - Docount
System 3
4-17
RV8 Barracuda
The Special Modes are set with a bit-masked pattern. For example, to set the
trigger mode using a zTRGA the value for the Special Mode would be set to 1 +
16 or “17”. To use the Mtrig function the value would be 1 (DoCount) + 16
(UseZTRGA) + 128 (MTRIG) or “145”.
DoCount
Enable DoCount to use the trigger mode. If this is not enabled then the device is
in free-run mode.
AutoClr
AutoClr works in trigger mode. AutoClr clears the output of the DAC's to zero after
the last value is played. Otherwise the output of the DAC is set to the last value
converted.
Trigger Mode
In trigger mode the circuit only runs after it has been triggered. After a trigger it
runs for set number of samples and then stops.
Using the trigger mode requires three steps:
1. Set the value of the Special Mode parameter.
This value is a bit-masked value. To calculate the value needed sum the
individual bit-masks (see above). The bit-masks include DoCount (1) the
trigger mode (16, 32 or 64 depending on what trigger option) and possibly
enabling MTRIG (128).
Bit
Number
Enabled
Value
Name
Function
0
1
DoCount
Sets up system to run under trigger mode.
1
2
AutoClr
Clears the DAC out buffers after a trigger event.
2
4
TickOut
Sends a pulse at the beginning of each tick period
on Digital Out 7. Pulse length is 40 nanoseconds.
3
8
ClkOut
Sends pulses at 1/2 the clock frequency (25 MHz).
4
16
UseZTRGA
Starts the Barracuda when a ZtrgA goes high. Only
works in the trigger mode (must also have bit-
number 1 enabled).
5
32
UseZTRGB
Starts the Barracuda when a ZtrgB goes high. Only
works in the trigger mode (must also have bit-
number 0 enabled).
6
64
UseEXTR
Starts the Barracuda using the external trigger. Only
works in the trigger mode (must also have bit-
number 0 enabled).
7
128
MTRIG
Enables multiple trigger mode. Users can repeatedly
trigger the Barracuda without stopping and rerunning
the circuit. 0=Very Large Number of Triggers