CMX808AE3 CML Microcircuits, CMX808AE3 Datasheet - Page 10

• Manufacturer Part Number: CMX808AE3
• Description: Family Radio CTCSS Type 2 Encoder and Decoder
• Manufacturer: CML Microcircuits

Family Radio CTCSS 'Type 2' Encoder and Decoder
CTCSS TX FREQUENCY Register (Hex address $83)
This is a 16-bit register. Byte (1) is sent first. When the CTCSS transmitter is enabled, the bits 0 to 12 control
the frequency of the transmitted CTCSS tones according to the formula below.
where A is the binary number programmed into the 13 bits.
When Bit 7 (in the first 8 bits) is set to "1" the tone output is set at V
number "A" programmed. When Bit 7 is "0" the programmed tone is set on the output. Programming bits 0 to
12 to "0" sets the output to V
CONTROL register $80).
CTCSS RX PROGRAM Register (Hex address $84)
This is a 16-bit register. Byte (1) is sent first. The two bytes are used to program the centre frequencies of up
to 7 tones in the sub-audio band that will be decoded by the receiver.
Each tone is identified by its address in Bits 6, 5 and 4 of byte (1). The remaining 12 bits contain the data
representing the tone frequency according to the formula below. If a tone is not required the 12 bits should be
set to zero.
Bit
The Hex address represented by Bits 6, 5 and 4 in byte (1) is used as the code to indicate which tone has
been decoded. This code appears in Bits 2, 1 and 0 of the SUB-AUDIO STATUS register $81. The 7
programmed tones use Hex addresses $0 - $6. Address $7 should not be used.
0
0
0
0
0
0
0
7
1999 Consumer Microcircuits Limited
Bit
0
0
0
0
1
1
1
6
Example: To program 100Hz when using the recommended 4.0MHz Xtal.
Thus the 12-bit code is 010111001111.
Bit
0
0
1
1
0
0
1
5
\ N =
\ R =
Bit
0
1
0
1
0
1
0
4
n =
r =
N is the binary representation of the
following decimal number (n):
n = INT (948982 x f
Byte 1
<----------------------- N ----------------------->
=
=
=
Bit
3
INT (948982 x 100 / 4.0 x 10^6)
INT (23.72) = 23
010111 (binary)
((237245 / 4.0 x 10^6) - (23 / (4 x 100))) x 8400
15.21 (round up if exactly halfway)
15
001111 (binary)
A
Bit
16 x f
2
f
XTAL
BIAS
TONE
Bit
. Powersave is achieved by disabling the Tx (Bit 7 in the SUB-AUDIO
(Hz)
1
TONE
(Hz)
/ f
Bit
0
XTAL
)
Bit
7
10
Bit
6
R is the nearest 6-bit binary
representation of (r), where:
r = ((237245/f
<----------------------- R ----------------------->
Bit
5
BIAS
Bit
4
Byte 2
XTAL
or NOTONE without regard to the
Bit
) - (n/(4 x f
3
Bit
2
TONE
Bit
))) x 8400
1
CMX808A
D/808A/5
Bit
0