Waveform Generator
Description
Page 5 of the upper I/O map provides control for the D/A waveform generator. The D/A waveform generator uses
an in-FPGA memory block of 1024 words to store D/A codes. The FPGA parses through this memory at a user-
programmable speed (or through manual/external trigger) while sending codes to the D/A converter. The generator
automatically stops if enhanced features are disabled.
The generator works on frames. A new frame is triggered from a programmable source (manual, counters, external,
etc.). For each frame, the FPGA sends a programmable (1, 2 or 4) number of D/A codes from the generator’s
memory bank to the DAC. This transfer is done in latched mode and the DAC is updated after all codes in a frame
are sent. The generator continues this process, incrementing through the memory until it reaches the end of the
buffer or reaches a programmable depth, where it wraps back to the beginning of the buffer and continues operation.
The generator can be paused, resumed or reset to the beginning of the memory bank at any time.
With the use of the memory block the D/A waveform generator can output consistent waveforms at a maximum
frequency of 100KHz. There are four different input sources available for the D/A waveform generator.
•
manual software trigger
•
counter 0 output
•
counters 1+2 output
•
external trigger
The memory block also allows a programmable depth which when hit, will wrap and return to the beginning. The
threshold ranges from 64 to 1024 and is programmable in multiples of 64.
Programming the D/A Waveform Generator
This section details how to program the D/A waveform generator through direct I/O without using the Diamond
Systems driver software. Please, note that the D/A waveform generator is an enhanced feature and enhanced
features must be enabled to access the feature.
The following steps, described in the following subsections, are used to programming the D/A waveform generator.
1. Enable enhanced features
2. Reset D/A waveform pointer
3. Latch D/A value
4. Store D/A values into buffer
5. Setup D/A wave form settings
6. Start D/A waveform generator
Enable Enhanced Features
Enable enhanced features as described in the Enabling Enhanced Features section of this document.
Reset D/A Waveform Pointer
Reset the D/A waveform pointer by accessing Page 5, Base+15, bit 2. Writing a 1 to this bit, causing the pointer to
start at the beginning, address 0.
Latch D/A Value
The procedure for latching a D/A value is nearly identical to the formula in the Generating An Analog Output
section of this document; the only difference is that instead of setting DASIM to 1, set DAGEN to 1. The D/A value
code must be computed for the desired voltage. From the computed value, obtain the LSB and MSB and add the
Diamond Systems Corporation
Poseidon User Manual
Page 91
