GC1115 Datasheet, PDF (62/80 Pages) Texas Instruments – Crest Factor Reduction Processor

GC1115
SLWS144 – FEBRUARY 2005
SOFT_COEF0..15 0xC2 – 0xD1 (194 – 209) Type: Read/Write
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Value at RESET: 0x0000
The sixteen SOFT_COEF registers hold the soft limiter’s taper table. The taper table contains 4, 8, or 16
normalized coefficients, whose values are scaled by a variable that is proportional to the size of the detected,
over-threshold soft limiter peak. SOFT_COEF0 at address 0xC2 is the smallest coefficient, while SOFT_COEFn
(n=3, 7, or 15) is the largest coefficient (near to a normalized value of 1.0). The soft limiter uses an internal,
normalized value of 1.0 at SOFT_COEFm (m = 4, 8, or 16) that is NOT stored in the SOFT_COEF taper table.
The taper table’s values are applied to the N samples before the detected peak, and again to the N samples
after the detected peak (N = 4, 8, or 16). Please refer to the section of this document entitled Soft Limiter
Operation for a detailed description of the soft limiter taper table.
When SOFT_LENGTH[1:0] = 01, taper table uses SOFT_COEF0 to SOFT_COEF3
When SOFT_LENGTH[1:0] = 10, taper table uses SOFT_COEF0 to SOFT_COEF7
When SOFT_LENGTH[1:0] = 11, taper table uses SOFT_COEF0 to SOFT_COEF15
BITS
[15:0]
DESCRIPTION
Soft limiter taper table coefficient (unsigned, 16-bit value)
SOFT_TAB_SCALE 0xD2 (210) Type: Read/Write Value at RESET: 0xFFFF
The SOFT_TAB_SCALE register contains the soft limiter’s lookup table scale factor. For a desired shift value of
N bits, SOFT_TAB_SCALE should be set to N – 17. The valid range for SOFT_TAB_SCALE is 0 to 15, encoded
in the 4 LSBs.
BITS
[3:0]
[15:4]
DESCRIPTION
Soft limiter lookup table scale factor (# bits to shift, 0 to 15)
Reserved
SOFT_INVGAIN0..31 0xD3 – 0xF2 (211 – 242) Type: Read/Write Value at RESET: 0x000
The thirty-two SOFT_INVGAIN registers hold the soft limiter’s inverse gain lookup table. The taper table contains
31 inverse gain values between 1.0 and g, where g is the maximum expected over-threshold value. For example,
if the soft limiter expects to see a peak after PDC Stage 4 that is at most 50% higher than the SOFT_TSQD
threshold, g would be set to 1.5. SOFT_INVGAIN0 (0xD3) contains the smallest inverse gain value.
SOFT_INVGAIN31 contains the largest inverse gain value. Please refer to the section of this document entitled
Soft Limiter Operation for a detailed description of the inverse gain lookup table.
BITS
[15:0]
DESCRIPTION
Soft limiter inverse gain lookup coefficient (unsigned, 16-bit value)
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