8.6.60 FREQA0 Register (Address = 0x220) [reset = 0x0]
FREQA0 is shown in Figure 83 and described in Table 119.
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NCO Frequency (Channel A, Preset 0) (default: 0xC0000000)
Figure 83. FREQA0 Register
31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
FREQA0 |
R/W-0x0 |
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Table 119. FREQA0 Register Field Descriptions
Bit |
Field |
Type |
Reset |
Description |
31:0 |
FREQA0 |
R/W |
0x0 |
The following description applies to FREQA0 thru FREQA3 and FREQB0 thru FREQB3.
The NCO frequency (FNCO) is:
FNCO = FREQA0 * 232 * FADC
FADC is the sampling frequency of the ADC. FREQA0 is the integer value of this register. This register can be interpreted as signed or unsigned (both interpretations are valid).
Use this equation to determine the value to program:
FREQA0 = 232 * FNCO /FS
If the equation does not result in an integer value, you must choose an alternate frequency step (FSTEP) and program the NCO_RDIV register. Then use one of these equations to compute FREQA0:
FREQA0 = round(232 * FNCO/FS)
FREQA0 = round(225 * FNCO/FSTEP/NCO_RDIV)
Changing this register after the NCO has been synchronized is running will result in non-deterministic NCO phase. If deterministic phase is required, the NCO should be re-synchronized after changing this register.
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