ERM HR C6000, Руководство пользователя

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6.1.4 2-tone send
The 2-tone signal has an in-band tone signal and an IDLE gap to form a tone sequence. Take the
EIA standard as an example. Each group of tones has a duration of 33ms and an IDLE gap of zero.
However, considering compatibility with other standards, software is available for signal length and
IDLE gap duration. As shown in the figure below, the switching between the tone signal and the
IDLE gap is achieved by the combination of the timing module and the path selection module.
Selcall tone occurs after the PTT is pressed and before the audio signal is transmitted. Selcall tone is
weighted by modulation factor and output after FM modulation.
Figure 6.8 2-tone Transmit Block Diagram
The detailed usage is detailed in Appendix A2.2.4.
6.1.5 5-tone send
5-tone is sent in the same way as 2-tone, with different register control bits to distinguish. The
detailed usage is detailed in Appendix A2.2.5.
6.2 FM reception
When configuration register 0x60=0x00, HR_C6000 is in receive mode. The HR_C6000 filters and
receives the received IQ (or intermediate frequency) signal and sends it to the FM processing
module. The phase-detected signal is filtered by an audio filter and then processed by Codec after
an optional de-emphasis and decompression module.
The above analog channels mainly support the reception of voice and signaling such as analog
voice, analog/digital sub-tone (CTCSS and CDCSS), DTMF, 2-tone/5-tone and MSK.
Filter
HR_C6000 provides two sets of low-pass filters in the FM receive processing channel, 2.55KHz
and 3KHz low-pass filters, of which 2.55KHz can be used for 12.5KHz channel spacing; 3KHz
low-pass filter is usually used for 25KHz channels interval. It can be selected by configuring the
0x34 register.
The HR_C6000 provides an optional de-emphasis module that meets the TIA requirements. The de-
emphasis module processes audio signals in the 300Hz to 3000Hz band at -6dB/Oct. The de-
emphasis module can be turned on by configuring register 0x34[5]=1'b1.
OMISSIS
Figure 6.9 De-emphasis frequency response curve
Selcall tone tone
generation module
IDLE
Path selector
Timing module
FM modulation
Modulation coefficient
weighting