AN2274 Freescale Semiconductor / Motorola, AN2274 Datasheet - Page 17

• Manufacturer Part Number: AN2274
• Description: Generic Tone Generation on the StarCore SC140 Core
• Manufacturer: Freescale Semiconductor / Motorola

3.3.2 MF-R2 Frequency Accuracy Test
The module capabilities were tested on the most constraining standard for frequency accuracy: MF-R2 signaling
defined in the ITU-T Recommendation Q.454 [7]. A deviation of up to 4 Hz is tolerated on generated frequencies.
Each frequency is measured with an 8192 point Hanning windowed FFT. At an 8 kHz sampling rate, the resulting
accuracy is smaller than 1 Hz. In Table 3 and Table 4, an error of 0 Hz means that the test is unable to detect any
frequency deviation.
All tests of the tone generator passed. Our results indicate that the proposed tone generation module complies with
the requirements for frequency accuracy of the ITU-T Recommendation Q.454 for MF-R2.
Freescale Semiconductor
F0
F1
F2
F3
F4
F5
F0
F1
F2
F3
F4
F5
Frequency (Hz)
Frequency (Hz)
Generic Tone Generation on the StarCore™ SC140/SC1400 Cores, Rev. 1
1380
1500
1620
1740
1860
1980
1140
1020
900
780
660
540
Table 2. Digital Oscillator Algorithm for DTMF Generation
Frequency (Hz)
Table 4. Backward Frequencies Test
1209
1336
1477
Table 3. Forward Frequencies Test
400
697
770
852
941
Frequency (Hz)
Frequency (Hz)
Measured
Measured
1379.6
1499.7
1619.8
1740.0
1859.1
1979.2
1139.3
1019.2
900.0
779.9
659.7
539.6
Precision (Percent)
Error (Hz)
Error (Hz)
0.4
0.3
0.2
0.0
0.9
0.8
0.7
0.8
0.0
0.1
0.3
0.4
Using and Testing the Generic Tone Generator
0.12
0.08
0.16
0.14
0.03
0.06
0.05
0.07
R2 Test
R2 Test
PASS
PASS
PASS
PASS
PASS
PASS
PASS
PASS
PASS
PASS
PASS
PASS
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