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Two-way Radio Processor IC Offering Voice, Signalling and Data Functions

CMX7031 and CMX7041


Features:
7031/7041FI-1.x:

  • Full Audio Baseband Processor with Selectable Processing Order
  • Voiceband and Sub-audio Signalling
  • 1200/2400 bps FFSK/MSK Freeformat Data
  • NOAA and NWR Operations

7031/7041FI-2.x:

  • 4.8 and 9.6 kbps 4-Level FSK Data with Freeformat and Packet Modes

7031/7041FI-3.x:

  • 4.8 and 9.6 kbps C4FM Data with Freeformat and Packet Modes

7031/7041FI-4.x:

  • 1200bps AFSK Modem
  • 9600bps GMSK Modem

Applications:

  • PMR and LMR Systems
  • Trunked Radio
  • Marine, Aviation and Amateur Radio
  • National Weather Radio (NWR)

Supply Requirement:

  • 3.0 to 3.6 V Power Supply

The CMX7031 and CMX7041 are half-duplex processor IC platforms built on FirmASIC technology that are suitable for use in multi-standard analogue Two-way Radio (TWR) systems.

FirmASIC component technology allows on-chip sub-systems to be reconfigured by a Function Image (FI): this is a data file that is uploaded during device initialisation that defines the device's function and feature set.

The CMX7031/CMX7041 enable a revolutionary new platform approach to radio design, enabling multi-mode analogue two-way radios to be developed based on a single radio platform, conforming to many systems: PMR, LMR, Trunking, Marine, Aviation, Amateur radio, NOAA weather radio and packet data radio.

To enable full control of the radio functions and minimise the overall chip count, two user programmable system clock outputs are provides along with auxiliary ADC and DAC blocks. A user-programmable PLL, driven from the Xtal/reference clock input, generates all internal clocks and allows one clock source to be internally reused for both baseband and RF synthesiser functions (for CMX7031 only). A flexible power control facility allows the device to maximise powersaving whilst not processing signals or when specific functions are not enabled.

New Enhancements:

  • Marine DSC Expansion Sequences
    • Enables precise position using marine DSC
  • Best-in-Class CTCSS Performance
    • Exceeds TIA-603 requirements for CTCSS squelch opening SINAD
    • Improved performance of phase shift detector for squelch tail elimination
    • Meets subaudible signalling requirements of TIA-603
  • SPI-Codec Routing Option
    • Mic and speaker paths can be intercepted and routed via the SPI port for external processing
    • Output format is 16-bit PCM at 8k samples/s (only available when 7031/7041FI-1.x is loaded into the CMX7131/CMX7141 devices)

Function Image Available:

Description Function Image
Multi-mode Analogue TWR Processor 7031/7041FI-1.x
4-level FSK Data Modem 7031/7041FI-2.x
C4FM Data Modem 7031/7041FI-3.x
Amateur Radio AX.25 Modem 7031/7041FI-4.x

Block Diagram

CMX7031/7041 System Diagram

Multi-mode Analogue TWR

Full-function, half-duplex, audio, signalling and data processing implementation for professional radio and leisure TWR radios: Public Mobile Radio (PMR)/Land Mobile Radio (LMR), Trunking, General Mobile Radio Service (GMRS), Family Radio Service (FRS), PMR446, and Multi-Use Radio Service (MURS) and Marine VHF, Aviation and Amateur radio products.

Concurrent sub-audio band and in-band signalling (best-in-class CTCSS performance) complete audio processing and a comprehensive FFSK/MSK free-format synchronised data mode, utilising CRC, FEC, interleaving and scrambling. modem implementation.

4-level FSK Data Modem

General purpose 4.8 and 9.6 kbps 4-level FSK data modem with freeformat and synchronised data modes.

C4FM Data Modem

General purpose 4.8 and 9.6 kbps C4FM data modem with freeformat and synchronised data modes.

Amateur AX.25 Data Modems

Combined 1200bps AFSK modem and 9600bps GMSK modem, specifically targetted at providing a universal data modem solution for amateur AX.25 packet data.

Design Support Information

 

7031/7041 FAQ
 

Tx and Rx FFSK Data Operations
Q. Is there a recommended procedure for handling FFSK/MSK data in transmit or receive modes when using the CMX70x1 (7031/7041FI-1.3) Two-Way Radio Processor ICs?

A. The linked pdf document provides an overview in the form of flow charts that illustrate which C-BUS registers need to be written-to and read-from when attempting a data transmission. It is indicative only and provides a minimum set of reads/writes to achieve successful data transfer.
[CMX70x1 Tx and Rx FFSK Data Operations]


Function Image 1.x - Auxiliary ADCs
Q. Are there any differences between the CMX70x1 FI - 1.x and the CMX88x series of devices in the way the AuxADC handles interrupts when a signal passes through the high and low threshold points?

A. The threshold facility allows the relevant devices to trigger an interrupt when a signal exceeds the high threshold limit or falls below the lower threshold limit. This is a useful feature when trying to detect changes in received signal strengths or voice activity for example. These thresholds are programmable which allows a lot of flexibility when designing a system.

Please note though that there is a subtle difference between the way the CMX70x1 FI - 1.x and the CMX88x series of devices handle the resultant interrupts. The following link will take you to an illustration of how interrupts are handled. [Auxiliary ADC Interrupts]


Scrambling
Q. Can you give me any information on the use of scrambling when using these products?

A. In order to achieve reasonable intelligibility of recovered scrambled/descrambled speech, the limitations detailed in the linked document should be considered. [Frequency Inversion Scrambling]


FI-1x

Q. I am about to start to use the CMX7041 in an application that uses CTCSS and FFSK data, do you have a worked example or illustration that I can refer to?

A. The following link will take you to a document that includes 4 basic examples both in transmit and receive. Signal paths and C-BUS register settings are shown for clarity.
[view document]


FI-2x

Q. I am about to evaluate the CMX70x1 FI2.0 (4FSK Modem) using the PE0201, what recommendations can you give me?

A. Operation is straightforward when following the instructions in the user manuals and FAQs, however a modest modification to the PE0201 is recommended.

The baseband signal requires a Tx-to-Rx channel with a relatively flat frequency response. To achieve this with the PE0201 kit from the default build will require the removal and replacement of certain capacitors.

  • C21 and C22 on the Mod1 and Mod2 paths should be removed
  • C11 at the discriminator input must be replaced by a zero ohm link
  • The removal of C17 may also benefit performance
  • All other components may remain the same

Note: If evaluating the 7041FI-2.x with a PE0401 kit the same modifications should be made.


FI-3.x modified: 11/05/07

Q. I am about to evaluate the CMX70x1 FI3.0 (C4FM Modem) using the PE0201 what recommendations can you give me?

A. Operation is straightforward when following the instructions in the user manuals and FAQs however a modest modification to the PE0201 is recommended.

The baseband signal requires a Tx-to-Rx channel with a relatively flat frequency response. To achieve this with the PE0201 kit from the default build will require the removal and replacement of certain capacitors.

  • C21 and C22 on the Mod1 and Mod2 paths should be removed
  • C11 at the discriminator input must be replaced by a zero ohm link
  • The removal of C17 may also benefit performance
  • All other components may remain the same

Note: If evaluating the 7041FI-2.x with a PE0402 kit the same modifications should be made.


Function Images
Q.
How long does it take to download a typical Function Image (FI) to a member of the CMX70xx family of devices?

A. The largest factor in overall Function Image (FI) download time is the main sequence of writing words to the IC's programming register ($C8).

We will consider the repetitive nature of the recommended sequence in the linked illustration.
We can see that:

Download Time = FI word count x (TREAD + TWRITE + TMEM + TREG).

Where:

  • TREAD and TWRITE are largely determined by C-BUS sclk speed. Up to a maximum of 5Mbps
  • TMEM is determined by host processor memory access time. Dependent on processor speed and latency etc. Much will depend on whether the host processor is only processing the FI download or not. Concurrent processing on the host is not recommended when downloading the FI.
  • TREG is determined by the local clock or crystal source (and sys clock settings)

For a 6.144MHz clock we can approximate TREG ˜ 5.3us
For a 19.2MHz clock we can approximate TREG ˜ 1.6us

In evaluation it was shown that not using interrupts but polling the Status Register until the programming flag is set ($C6, b0), achieved best overall performance.

This approach is further enhanced if the time taken by 8 x C-BUS sclk cycles is greater that the time taken for the CMX70xx to process a single prewritten Word.
Or: 1/Sclk x 8 < TREG

This process then takes advantage of the fact that the times TREAD and TREG are independent processes and can take place concurrently. The following link takes you to an illustration of this improved method.

Example:
Assume a maximum FI size of 23kWords, 2Mbps sclk, 6.144MHz clock source and a host processor latency of 10us. The calculation includes the improvement introduced by polling only (interrupt is masked) so TREG has been removed.

Download Time = FI word count x (TREAD + TWRITE + TMEM)

1/Sclk x 8 = 4us which is less than 5.3us so the above equation is valid

Therefore:
Download Time = 23k x (12us + 12us + 10us) = 800ms

Notes:

  1. Power cycling, resets of the CMX70xx will also add to the overall time. However under normal circumstances a FI re-write does not require power cycling a reset procedure will be sufficient.
  2. In practice real FI sizes will be less than the maximum 23Words, typical sizes will be half this figure. Please refer to the relevant FI pages on the CML web portal (My_CML).

Conclusion
It can be seen that FI downloads can reliably be written in no more than a few seconds. Updating an existing FI with a new variant will take no longer than the initial install as the RESET procedure is very quick.

The largest delay to FI installation potentially is the host processor latency and the speed at which the C-BUS sclk is driven.


Q. What are the NWR functions?

A. A new feature is the provision of NWR, which allows customers in the USA to decode and respond to the NWR / NOAA weather broadcasts.

The new signal processing architecture of the CMX7031/CMX7041 allows this signal to be decoded in parallel with the other PMR / FRS signal processing.


Q. What are the C-BUS differences between the CMX7031/CMX7041 and the 88x series?

A. The CMX7031 and CMX7041 are based on the successful 88x series of devices but offer some significant improvements and many functional enhancements.

The flexibility of the FirmASIC platform allows for further development and features can be added as required.

Some changes have been made to the C-BUS host interface to accommodate the complete set of features from the 88x series and the additional features of the 7031, however, whenever possible, backwards compatibility has been maintained to ease the transition to the new family.

The AuxADC/TX Mod Mode, Analog Output Gain and Input Gain registers ($A7, $B0, $B1) must be used to set up the Audio routing through the device.

The Powerdown, Mode Control, Interrupt Mask and Interrupt Status registers ($C0, $C1, $CE, $C6) have been changed to support the new functionality. The sub-audio signalling (CTCSS and DCS) control and reporting has been rationalised to use the Audio Control and Tone Status registers ($C2, $CC).

The In-band signalling has been expanded to include DTMF Rx and uses Tx In-Band tones and Tone Status registers ($C3, $CC). All In-band tones activity is signalled to the host via IRQ bit13 (this includes DTMF Rx).

The frequency resolution of the Selcall and Custom tones has been improved, but the consequence is that the values used in the Program Registers are different from the 88x series. New Program block registers have been introduced to support the new and improved functionality.


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