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Jason
bf63d64533
The coefficient ROM has a deliberate positive DC pre-emphasis. Sum of 32 signed coefficients = 231,944; with the output slice at accumulator[34:17] (effective Q17), DC gain = 231944 / 2^17 = 1.7696 = +4.96 dB. Bit-exact against the in-header golden-model line (DC=5000 → 8847). The +4.96 dB pre-emphasis compensates the upstream 4-stage CIC's ~3-4 dB passband droop. Without this note in the header, a future engineer rebuilding the filter from a clean FIR design tool would silently lose the pre-emphasis; AGC/saturation budgets in downstream stages must also account for the +4.96 dB rather than assume 0 dB. Audit's original "+7 dB" estimate was directionally correct but quantitatively wrong (no Q-format reconciles to +7 dB; Q15 → +17 dB, Q16 → +11 dB, Q17 → +4.96 dB). Documented at the verified +4.96 dB. No coefficient or RTL change. Verified: full FPGA regression 41/41 PASS, 0 lint errors (FIR Lowpass: 13 checks PASS).