Audio Signaling Processor
13
MX803A PRELIMINARY INFORMATION
1996 MX
COM, INC.
Tele: 800 638 5577 910 744 5050 Fax: 910 744 5054
Doc. # 20480122.003
5.2.3.3 Calculations
As seen in Table 4 and Table 5, 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
Input Data Word (bits 0 to 12)
=
=
=
f
TONE
1 or 2
f
XTAL
“A” or “B”
f
=
f
'A' or 'B' Hz or Input 'A' or 'B' =
4
f
×
4
f
Hz
TONE
XTAL
TONE
×
5.2.3.4 Tx Tone Frequencies
With reference to Table 4 and Table 5, 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 7.
5.2.4 Read RX Tone Frequency Register
A/C 32
H
, followed by 2 bytes of Reply Data
5.2.4.1 Measurement of RX Signal Frequency S
IN
The input audio signal, S
IN
, is measured in the Frequency Counter over a specified measurement period (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
in the form of 2 bytes (1 and 0) as 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).
Complete
Input
Cycle
Complete
Input
Cycle
Complete
Input
Cycle
Complete
Input
Cycle
Complete
Input
Cycle
Measuring
Clock
Cycles
Measurement Period
N
R
FILTERED AUDIO INPUT SIGNAL
2 x S
INPUT
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
Extended Band Decode
=
=
=
9.125ms
18.250ms
9.125ms
Note
: See section 5.2.4.4 for calculation of measurement period (t) using a Xtal other than 4.032MHz.