4.4.3.2.1.3 DMDRA – Demodulator Data Rate on Path A

The target symbol rate for the receiving path A is configured in this register. This register must only be modified if the block receiving the settings is disabled (RDPR.PRPTA = 1). Modifying the settings during operation may lead to unstable operation.

Name:	DMDRA
Offset:	0x0A8
Reset:	0x00


Bit	7	6	5	4	3	2	1	0
	DMDNA[3:0]				DMAA[3:0]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0

Bits 7:4 – DMDNA[3:0] Demodulator Down-Sampling on Path A

Selects the down-sampling and cut-off frequency of the first stage of the data filter.

Table 4-12. DMDNA Setting versus Amplitude Threshold Scaling on Path A (ATSCAL_A)
DMDNA	ATSCAL_A
0	1
1	1
2	2
3	2
4	4
5	4
6	8
7	8
8	16

The recommended down-sampling for a target symbol rate is:

D M D N A = f l o o r [I d (20) + I d (\frac{C L K_B B}{S y m b o l R a t e P a t h A \times 128})] (18)

If the result is -1, set DMDNA = 0.

Equation parameters:
- SymbolRatePathA: Maximum expected symbol rate in Hz on the useful signal for path A
- CLK_BB: Baseband clock frequency in Hz. See equation (13) in Bandwidth Scaling. See Bandwidth Scaling in the Channel Filter from Related Links.
- ld(): Logarithm to the base 2

Bits 3:0 – DMAA[3:0] Demodulator Moving Average Data Rate Factor on Path A

Selects the moving average filter length for the data filter and initial data rate for the clock recovery on path A.

Table 4-13. DMAA Setting versus Moving Average Filter Length and Symbol Rate Factor on Path A (MAVFL_A, SR_F_A)
DMAA	MAVFL_A	SR_F_A
0	12	10
1	11	11
2	10	12
3	9	13
4	9	14
5	8	15
6	8	16
7	7	17
8	7	18
9	6	19
10	6	20
11	6	21
12	5	22
13	5	24
14	4	26
15	4	28

The recommended settings for this register are provided by the configuration tool after selecting the desired target data rate for path A. They can also be calculated by using this procedure:

Calculation of the symbol rate factor.

S R_F_A = r o u n d (S y m b o l R a t e P a t h A \times 2^{D M D N A} \times \frac{128}{C L K_B B}) (19)

Equation parameters:
- SymbolRatePathA: Maximum expected symbol rate in Hz on the useful signal for path A
- CLK_BB: Baseband clock frequency in Hz. See equation (13) in Bandwidth Scaling. See Bandwidth Scaling in the Channel Filter from Related Links.
- SR_F_A: Must be in the range of 10 to 28, if possible 10 to 19

For more details on finding the corresponding DMDNA setting, see DMDNA Setting versus Amplitude Threshold Scaling on Path A (ATSCAL_A) in the Demodulator Register Description from Related Links.

DMAA	MAVFL_A	SR_F_A
0	12	10
1	11	11
2	10	12
3	9	13
4	9	14
5	8	15
6	8	16
7	7	17
8	7	18
9	6	19
10	6	20
11	6	21
12	5	22
13	5	24
14	4	26
15	4	28

DMAA	MAVFL_A	SR_F_A
0	12	10
1	11	11
2	10	12
3	9	13
4	9	14
5	8	15
6	8	16
7	7	17
8	7	18
9	6	19
10	6	20
11	6	21
12	5	22
13	5	24
14	4	26
15	4	28

DMAA	MAVFL_A	SR_F_A
0	12	10
1	11	11
2	10	12
3	9	13
4	9	14
5	8	15
6	8	16
7	7	17
8	7	18
9	6	19
10	6	20
11	6	21
12	5	22
13	5	24
14	4	26
15	4	28