EV6240 Datasheet, PDF (18/47 Pages) CML Microcircuits – Opto-Isolated serial interface capability

Evaluation Kit for CMX624/CMX644A
EV6240
1.6.1.11 DTMF Decoding
An indication of the DTMF signal levels on either the 2 or 4 wire lines for each Modem are provided
at Bit 2 (Pin 4) and Bit 5 (Pin 7) of the PIC µC Port A. These µC pins can be re-
configured as ADC inputs and, with appropriate firmware, be used to decode the DTMF signal.
The DTMF signal level at the PIC µC inputs can be adjusted by changing components R40 (Modem
One) or R68 (Modem Two). The components R40 and R68 have been fitted with values to provide a
20dB voltage gain with respect to the signal level at RXO.
Note that this feature is not used by the current firmware revision.
1.6.2
Adjustments and Controls
Various line interface components around the evaluation devices are socketed to allow for user
adjustments. Discrete component sockets are also provided for Telco-specific components.
Miniature control switches are provided to select the required line interfaces (2-wire or 4-wire), on-
board crystals (3.5795MHz or 3.6864MHz), mode (operating or program) and serial interface
(normal or isolated).
1.6.3
Firmware Description
The source code for the PIC firmware is supplied as the file EF6240XX ASM.
Please note that there are two modes of operation for the Evaluation Kit.
Modem Mode allows one of the evaluation board modems to perform calling, answering and simple
data tests with a line simulator or external third party modem (not supplied).
Test Mode allows diagnostic and performance tests to be made on Modem One and/or Modem Two.
The firmware supplied in the PIC µC assumes the following configuration; 8 data bits, no parity, 1
stop bit and 19,200 baud with hardware handshake but without CR → CR/LF conversion.
The firmware only supports DTMF dialling.
The firmware routine run at start-up and reset performs the following important tasks:
Peripheral Interrupt Initialisation
µC ports and I/O direction initialisation
Serial Communication Interface (SCI) initialisation
Serial Peripheral Interface (SPI) initialisation
Loads Modem One and Modem Two with factory profile 0
Resets Modem One and Modem Two evaluation devices.
The message EF6240 Vx.x (where x.x represents the version number), will be displayed in the
terminal emulator window when these tasks have been completed.
AT command echoing is an option available in the firmware and involves echoing the received
characters sent by the PC. When echoing is enabled the firmware will send a LF character directly
after a CR character to ensure the terminal emulator display is legible.
The firmware also provides the option of sending result codes to the PC. These responses can be in
either an alpha or numeric (hex) form.
Simple data transfer using the terminal emulator involves the user entering text via the keyboard.
Downloading data may be achieved using the terminal emulator send text file facility. The µC
firmware does not support any send or receive data transfer protocols.
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© 1999 Consumer Microcircuits Limited
UM6240/3