Audio Signaling Processor
Page 13 of 26
MX803A PRELIMINARY INFORMATION
5.2.3.3 Calculations
As seen in Table 6 and Table 7, a binary number (“A” or “B” - bits 0 to 12) is loaded to the respective TX Tone
Generator. The formulas described below are used to produce the required output frequency.
Required TX Tone output frequency
Xtal/clock frequency
=
=
=
fTONE 1 or 2
fXTAL
Input Data Word (bits 0 to 12)
“A” or “B”
fXTAL
fXTAL
fTONE
=
Hz
or Input 'A' or 'B' =
Hz
4 × 'A' or 'B'
4 × f TONE
5.2.3.4 Tx Tone Frequencies
With reference to Table 6 and Table 7, while Input Data Words “A” or “B” can be programmed for frequencies
outside the stated limits of 208Hz and 3000Hz, any output frequencies obtained may not be within specified
parameters. See section 6.
5.2.4 Read RX Tone Frequency Register
A/C 32H, followed by 2 bytes of Reply Data
5.2.4.1 Measurement of RX Signal Frequency SIN
The input audio signal, S , is measured in the Frequency Counter over a specified measurement period
IN
(9.125ms or 18.250ms).
The measuring function counts the number of complete input cycles occurring within the count period and then
the number of measuring clock cycles necessary to make up the period.
When the count period of a successful decode is complete, the RX Tone Measurement bit in the Status
Register and the Interrupt bit are set.
The RX Tone Frequency Register will now indicate the signal frequency S in the form of 2 bytes (1 and 0) as
IN
illustrated in Figure 6.
Note: The following measurements are based on a clock frequency of 4.032 MHz. See section 5.2.4.4 for a
scaling formula for other crystal values).
Measurement Period
Measuring
Complete
Input
Cycle
Complete
Input
Cycle
Complete
Input
Complete
Input
Complete
Input
Clock
Cycles
Cycle
Cycle
Cycle
FILTERED AUDIO INPUT SIGNAL 2 x S INPUT
N
R
Figure 5: Measurement of an Rx Frequency
5.2.4.2 The Integer (N) - Byte 1
This is a binary number representing twice the number of complete input audio cycle periods. It is counted
during the specified measurement period (t), when (t) is:
High Band Decode
Mid Band Decode
=
=
=
9.125ms
18.250ms
9.125ms
Extended Band Decode
Note: See section 5.2.4.4 for calculation of measurement period (t) using a Xtal other than 4.032MHz.
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