Histogram Target Table

#4 & #5 as indicated in the Histogram Max Target table. Due to a high data resolution and relatively slow data rate, a relatively long period of time is required for generating histogram data from the DRCS with high decimation values in the DDC. Under some circumstances, the serial PC interface will time out. The program detects this condition and queries the user to continue. Click “Yes” to continue and wait for the Progress Bar to run to completion. Be patient, it could take several minutes depending on the input amplitude and DDC decimation value and Histogram Target Value. The last mode description, Debug Histogram, provides further description of the output ﬁle generated by the hard- wired histogram generator.

gram data of the DRCS output generated by the Capture Board at an input frequency of 150MHz and 16dBm in amplitude using all the default DRCS set- tings. The data source was the DDC serial output (Capture Histogram mode was used where Fsample is 270KHz) and therefore took several minutes to collect. In this scenario the 24-bit data source resolution is truncated to the 15-bits (32K) of available SRAM. The histogram peak target was set to 16K which required over 16 million data points be processed for the input level of -2dB below full scale. The number of data points is proportional to the Max Target and the amplitude range of the data (the X- axis). The “Plot Data” menu function of the analysis tools was used to generate the actual Matlab plot ﬁgure.

		Histogram
SW1; #4	SW1; #5	Target Value
0	0	16K
0	1	8K
1	0	4K
1	1	2K

3.Capture Debug mode conﬁgures the Capture Board to collect data from the DRCS evaluation board’s 20-bit parallel debug data bus. Because the FIFO memory is limited to 18 bits, the user is given the option to collect the full data width in the SRAM by selecting the 20 Bits menu button. As previously mentioned, parallel data which runs at the full clock speed (i.e. Mixer Out at Debug port) gets deci- mated by 6 due to the fact that the FPGA requires multiple clock strobes to address and write data into the SRAM. Choosing the Upper 18 Bits option will use the high speed FIFO for the memory element and collect a contiguous 32K block of data. The Debug data port provides users access to nodes internal to the CLC5902 DDC. Refer to the DRCS Evaluation Board User Manual and CLC5902 data sheet for more detailed information.

4.Histogram Debug mode conﬁgures the Capture Board to generate a histogram ﬁle using the parallel data as the source. The hardware requires multiple clock strobes to increment each SRAM value. Even though the data used is not a contiguous block, the probability density information is retained. The SRAM depth (32K) is used to store the data bin values; therefore, the histogram generator is limited to 15-bits of resolution (there are only 32,767 bins). The values of all 32K bins will be read out of the SRAM and sent out to the users PC regardless of the resolution of the data source. The DRCS Debug data will be displayed at the 15-bit resolution limit (this is also the case for the DRCS 24-bit Serial Out data) and the histogram will be centered about 16,384 assuming there is no intentional DC offset. The following ﬁgure displays the sine wave histo-

DRCS Evaluation Setup Sanity Check

The following discussion is to conﬁrm the DRCS evaluation setup. The example uses a Fourier analysis of a simple, single tone, sinusoidal IF input to the DRCS. It is assumed that Setup.exe on the evaluation kit’s CDROM has installed the necessary ﬁles in the user’s PC and the DRCS and Data Capture hardware is conﬁg- ured as shown in the diagram at the front of Section III. It is also assumed that Matlab (version 5.1 or higher) is available. Reconﬁguration of the DRCS through its Con- trol Panel software is not required for these two tests. The DRCS default values contained within the micro-control- ler with SW2:1-8 = OFF (on DRCS board) will conﬁgure the CLC5902 with the proper values. If the power has been applied while in another state or if the user has RESET the micro-controller with a different switch set- ting, then set the SW2 switches to OFF and press the RESET button on the DRCS Evaluation board.

**Apply an IF input signal to the AIN1 jack on the DRCS Evaluation board at 150MHz and 0dBm. The DDC mixer is set to -5.97MHz which brings the aliased (Fclk ADC = 52MHz; 3rd alias = 156MHz) signal down to +30KHz. The DDC then ﬁlters and decimates the data and sends it out the serial port (AOUT) in the “packed”, “muxed_mode” format.

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