Figure 7-10 shows the location of the test pattern blocks within the device. When the digital
signal processing (DSP) features are disabled (D2 of 0x24), a test pattern block can
be enabled to replace the ADC data. Similarly, when using the DDC, a test pattern is
available to replace the DDC data.
Note: No test pattern block is available when the DSP features are
enabled and the DDC is not used.
Each test pattern block has the
capability to generate one of the following outputs:
- Ramp pattern with
programmable step size set by PAT_DATA.
- Constant pattern with a
programmable custom pattern set by PAT_DATA.
As shown in
Figure 7-10, there are two test pattern blocks, test pattern 0 and test pattern 1. The test
pattern mode for each block can be configured via D7:D5 and D4:D2 of 0x16. A shared
set of data bits (PAT_DATA) is given to the test pattern blocks and this data is
used as ramp pattern step size and/or the constant pattern. The PAT_DATA is an
18-bit value located across three different registers: D17:D16 in 0x16, D15:D8 in
0x15, and D7:D0 in 0x14. The PAT_DATA is MSB aligned. For example, if the device is
configured for 14-bit resolution and constant pattern, only the top 14-bits of the
PAT_DATA are used for the constant pattern. Additionally, in ramp mode, the test
pattern counter operates at a 18-bit resolution; therefore, the ramp pattern step
size must be configured based on the desired resolution and the step size at that
resolution.
- The test pattern data must be configured to the following for
a step size of one at each resolution:
- 0x00001: 18-bit output
resolution
- 0x00004: 16-bit output
resolution
- 0x00010: 14-bit output
resolution