MX COM Inc CMX808AE2 Datasheet

DATA BULLETIN

CMX808A

1999 MX-COM, Inc. www.mxcom.com tel: [phone] 744 5050 fax: [phone] Doc. # 20480199.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

Family Radio Service

CTCSS Processor

PRELIMINARY INFORMATION

Features

•

Rapid multi-tone CTCSS decoder
supports new end user features

•

Fast Tone Decode (150ms)

•

Supports Tones from 62.5Hz to 251Hz

•

Integrated 32 Step Digital Volume
Control (-48.0dB to 0dB + Off)

•

Tone Cloning Capabilities

•

Sub-Audio Tone Rejection Filter

•

Low Power 3.0V to 5.5V Operation

•

Very small 20-pin TSSOP Package

•

4.0MHz Xtal/Clock Oscillator

Applications

•

Family Radio Service (FRS) Radios

•

Amateur Radio Equipment

•

General Mobile Radio Service (GMRS)

•

Short Range Business Radio

MODULATOR

DISCRIMINATOR

HOST

µC

KEYPAD

DISPLA Y

RADIO

CMX808A

RF

Tx

SERIAL 'C-BUS'

DATA & CONTR OL

Rx

FAST CTCSS

AUDIO FILTER

VOLUME CONTROL

The CMX808A is a programmable CTCSS encoder/decoder optimized for Family Radio Service transceivers
through a combination of leading edge performance, low cost, small size, and low power. With rapid
response time and the ability to decode one-of-many possible tones, the decoder enables practical tone
scanning to allow an FRS radio to quickly decode received CTCSS tones by 'listening' to the CTCSS tone
transmissions of other FRS radios. This feature can be used to:

1. Readily support both individual (one person) and group (e.g. children vs. adults) call codes.

2. Support quick and automatic resolution of radio user frustration caused by mismatched CTCSS tone
configurations in CTCSS-based FRS radios. In some cases, this approach can be used to match
CTCSS tone decoder configurations to different vendors' CTCSS-based FRS radios when supported
tone sets are not clearly documented or well understood.

With integrated digital volume control and a simple serial control interface, the CMX808A features very low
power consumption and small size. The CMX808A requires a 3.0V to 5.5V power supply and is available in
the following packages: 20-pin TSSOP (CMX808AE3) and 24-pin PDIP (CMX808AP4).

Family Radio Service CTCSS Processor 2 CMX808A Preliminary Information

1999 MX-COM, Inc. www.mxcom.com tel: [phone] 744 5050 fax: [phone] Doc. # 20480199.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

CONTENTS

Section Page

1 Block Diagram................................................................................................................3

2 Signal List.......................................................................................................................4

3 External Components....................................................................................................6

4 General Description.......................................................................................................7

4.1 Software Description ........................................................................................................... 7

4.1.1 Address/Commands...............................................................................................................7

4.1.2 Write Only Register Description .............................................................................................7

4.1.3 Read Only Register Description...........................................................................................12

5 Application Notes ........................................................................................................15

5.1 General.............................................................................................................................. 15

5.2 Transmitter ........................................................................................................................ 15

5.3 Tx Tone Table ................................................................................................................... 16

5.4 Receiver (Decode)............................................................................................................. 16

5.5 Rx Tone Table................................................................................................................... 17

6 Performance Specification..........................................................................................18

6.1 Electrical Performance ...................................................................................................... 18

6.1.1 Absolute Maximum Ratings.................................................................................................. 18

6.1.2 Operating Limits...................................................................................................................18

6.1.3 Operating Characteristics.....................................................................................................19

6.1.4 Timing Diagrams..................................................................................................................21

6.2 Packaging.......................................................................................................................... 22

MX-COM, Inc. reserves the right to change specification at any time and without notice.

Family Radio Service CTCSS Processor 3 CMX808A Preliminary Information

1999 MX-COM, Inc. www.mxcom.com tel: [phone] 744 5050 fax: [phone] Doc. # 20480199.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

1 Block Diagram

CLOCK OSCILLATOR

AND DIVIDERS

SUB AUDIO

LPF

AUDIO

FILTER

CTCSS Tx TONE

GENERATOR

'C-BUS'

INTERFACE

AND

CONTROL

LOGIC

A to D

CONVERTER

CTCSS TONE

DECODER

V

BIASVSS

V

DD

C6

C4

TX AUDIO IN

TX AUDIO

INPUT

R1

-

+

CTCSSTx

AUDIOTx / Rx

RX AMP

Enable

V

BIAS

RXAMPOUT

RXAMPIN

C3

XT AL

XT AL/CLOCK

C5

R3

R4

C7

Input from

Demodulator

C1

C2

X1

C8

A/D CAP CTCSS Rx

TX SUB AUDIO OUT TX AUDIO OUT RX AUDIO OUT

VOLUME OUT

COMMAND DATA

REPLY DATA

CS

IRQ

SERIAL CLOCK

V

DD

R2

Enable

Volume

Control

VOLUME IN

Figure 1: Block Diagram

Family Radio Service CTCSS Processor 4 CMX808A Preliminary Information

1999 MX-COM, Inc. www.mxcom.com tel: [phone] 744 5050 fax: [phone] Doc. # 20480199.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

2 Signal List

Package /

Pin No

Signal

E3 P4 Name Type

Description

11

XTAL

output The inverted output of the on-chip oscillator.

2 2 XTAL/CLOCK input

The input to the on-chip oscillator, for external Xtal circuit or
clock.

3 3 SERIAL CLOCK input

The "C-BUS" serial clock input. This clock, produced by the
µC, is used for transfer timing of commands and data to and
from the device. See Figure 6.

4 4 COMMAND DATA input

The "C-BUS" serial data input from the µC. Data is loaded
into this device in 8-bit bytes, MSB (D7) first, and LSB (D0)
last, synchronized to the SERIAL CLOCK. See Figure 6.

5 5 REPLY DATA output

The "C-BUS" serial data output to the µC. The transmission
of REPLY DATA bytes is synchronized to the SERIAL

CLOCK under the control of the

CS

input. This 3-state
output is held at high impedance when not sending data to
the µC. See Figure 6.

66

CS

input

The "C-BUS" data loading control function: this input is
provided by the µC. Data transfer sequences are initiated,

completed or aborted by the

CS signal. See Figure 6.

77

IRQ

output

This output indicates an interrupt condition to the µC by
going to a logic "0". This is a "wire-ORable" output,
enabling the connection of up to 8 peripherals to 1 interrupt
port on the µC. This pin has a low impedance pulldown to
logic "0" when active and a high-impedance when inactive.
An external pull-up resistor is required. An interrupt is
effective if not masked out by the IRQ MASK (bit 0 in the
SUB-AUDIO CONTROL register $80).

88 NC

9NC

No internal connection. Do not make any connection to
these pins.

9 10 A/D CAP output

An internal reference voltage for the A to D converter,
decoupled to V

SS

by an external capacitor.

11 NC

No internal connection. Do not make any connection to this
pin.

10 12 V

SS

Power The negative supply rail (ground).

11 13 V

BIAS

output

A bias line for the internal circuitry, held at V

DD

/2. This pin
must be decoupled by a capacitor mounted close to the
device pins.

12 14 RX AMP IN input The inverting input to the Rx input amplifier.
13 15 RX AMP OUT output

The output of the Rx input amplifier and the input to the
audio filter section.

14 16 RX AUDIO OUT output Output of the Rx audio filter section.

17 NC

No internal connection. Do not make any connection to this
pin.

15 18 TX AUDIO IN input Input to the Tx audio filter section.
16 19 TX AUDIO OUT output Output of the Tx audio filter section.
17 20 VOLUME IN input Input to the audio volume control.
18 21 TX SUB AUDIO OUT output Output of the CTCSS tone generator.
19 22 VOLUME OUT output Output of the audio volume control.

Family Radio Service CTCSS Processor 5 CMX808A Preliminary Information

1999 MX-COM, Inc. www.mxcom.com tel: [phone] 744 5050 fax: [phone] Doc. # 20480199.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

Package /

Pin No

Signal

E3 P4 Name Type

Description

23 NC

No internal connection. Do not make any connection to this
pin.

20 24 V

DD

Power

The positive supply rail. Levels and voltages are dependent
upon this supply. This pin should be decoupled to V

SS

by a

capacitor.

Table 1: Signal List

Family Radio Service CTCSS Processor 6 CMX808A Preliminary Information

1999 MX-COM, Inc. www.mxcom.com tel: [phone] 744 5050 fax: [phone] Doc. # 20480199.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

3 External Components

V

DD

V

DD

V

SS

V

DD

V

BIAS

IRQ

XTAL

A/D CAP

SERIAL CLOCK

"C-BUS"

INTERFAC E

COMMAND DA TA

XTAL/CLOCK

RX AMP IN

R3

R4

R2

Input from
Demodulator

Tx Audio Input

CMX808AE3

TX SUB AUDIO OUT

C4

C8

C5

C3

C7

C6

REPLY DATA

CS

NC

RX AMP OUT

RX AUDIO OUT

VOLUME OUT

VOLUME IN

TX AUDIO IN

TX AUDIO OUT

1
2
3
4
5
6

8
9

10

11

12

13

14

7

20
19
18
17
16
15

XTAL

XTAL/CLOCK

C1

C2

X1

R1

Figure 2: Recommended External Components

R1 1M

: ±5% C4 0.1µF ±20%
R2 22k: ±10% C5 100pF ±20%
R3 100k: ±10% C6 0.1µF ±20%
R4 Note 1 ±10% C7 Note 1 ±20%
C1 22pF ±20% C8 0.1µF ±20%
C2 22pF ±20%
C3 0.1µF ±20% X1 Note 2 4.0MHz ±100ppm

Table 2: Recommended External Components

Recommended External Component Notes:

1. R3, R4, C5 and C7 form the gain components for the Rx Input Amplifier. R4 should be chosen as required
by the signal level, using the following formula:

R4

R3

- Gain =

C7 x R4 should be chosen so as not to compromise the low frequency performance of this product.

2. For best results, a crystal oscillator design should drive the clock inverter input with signal levels of at
least 40% of V

DD

, peak to peak. Tuning fork crystals generally cannot meet this requirement. To obtain

crystal oscillator design assistance, please consult your crystal manufacturer.

Family Radio Service CTCSS Processor 7 CMX808A Preliminary Information

1999 MX-COM, Inc. www.mxcom.com tel: [phone] 744 5050 fax: [phone] Doc. # 20480199.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

4 General Description

The CMX808A is a programmable CTCSS Processor for Family Radio Service, see Figure 1.
The receiver of the CMX808A decodes a user-programmable set of up to 7 tones with minimum software

intervention; the band-pass filter is designed to filter out the CTCSS sub-audio tones. A high-resolution tone
encoder performs accurate generation of CTCSS tones.

Each function, and the routing of signals, is flexible and may be configured or controlled by the user's
software.

4.1 Software Description

4.1.1 Address/Commands

Instructions and data are transferred, via "C-BUS", in accordance with the timing information given in Figure

6.

Instruction and data transactions to and from the CMX808A consist of an Address/Command (A/C) byte,
which may be followed by either:

(i) a further instruction or data (1 or 2 bytes) or
(ii) a status or Rx data reply (1 byte)

4.1.2 Write Only Register Description

HEX

ADDRESS/

COMMAND

REGISTER

NAME

BIT 7

(D7)

BIT 6

(D6)

BIT 5

(D5)

BIT 4

(D4)

BIT 3

(D3)

BIT 2

(D2)

BIT 1

(D1)

BIT 0

(D0)

$01

GENERAL

RESET

N/A N/A N/A N/A N/A N/A N/A N/A

CTCSS CTCSS DECODER BANDWIDTH

$80

SUB-AUDIO

CONTROL

TX

ENABLE

DECODER

ENABLE

MSB

BIT 3 BIT 2 BIT 1

LSB

BIT 0

0

CTCSS

IRQ

MASK

AUDIO ATTENUATION

$82

AUDIO

CONTROL

TX BPF

ENABLE

RX BPF

ENABLE

BPF

UN-

MUTE

MSB

BIT 4

BIT 3 BIT 2 BIT 1

LSB

BIT 0

Table 3: 8-bit Write Only Registers

HEX ADDRESS/

COMMAND

REGISTER

NAME

BIT 7

(D7)

BIT 6

(D6)

BIT 5

(D5)

BIT 4

(D4)

BIT 3

(D3)

BIT 2

(D2)

BIT 1

(D1)

BIT 0

(D0)

CTCSS TX FREQUENCY

CTCSS

TX FREQ.

(Byte 1)

CTCSS

TX

NOTONE

00

MSB

BIT 12 BIT 11 BIT 10 BIT 9 BIT 8

CTCSS TX FREQUENCY

$83

CTCSS

TX FREQ.

(Byte 2)

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1

LSB

BIT 0

CTCSS TONE ADDRESS CTCSS FREQUENCY

CTCSS RX
PROGRAM

(Byte 1)

0

MSB
BIT2

BIT 1

LSB

BIT 0

MSB

BIT 11 BIT 10 BIT 9 BIT 8

CTCSS FREQUENCY

$84

CTCSS RX
PROGRAM

(Byte 2)

BIT 7 BIT6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1

LSB

BIT 0

Table 4: 16-bit Write Only Registers

4.1.2.1 GENERAL RESET (Hex address $01)

The reset command has no data attached to it. It sets the device registers to zero (all powersaved) with the
exception of Bits 2, 1 and 0 of the SUB-AUDIO STATUS register $81.