The FX604 is a low power CMOS integrated circuit for the reception and transmission of asynchronous 1200bps data in accordance with CCITT V.23 and ETSI specifications. It is also capable of generating the 75bits/sec ‘back channel’.
The device incorporates an optional Tx and Rx data retiming function, removing the need for a UART in the associated µC when operating at 1200bps.
A line equaliser is incorporated into the receive path, controlled by an external logic level.
With a low voltage requirement of 3.0V, a low current sleeping mode and an operating current of 1mA typ. it is suitable for both portable terminal and line powered applications and may be used in a wide range of telephone telemetry systems.
Devices are available through our distributors below:
FX/MX604 and FX/MX614 FAQ
Q. 604 – Why do the FX604 and FX614 apparently receive data when there is no input signal? A. The FSK receiver of the FX604 and FX614 has a very high sensitivity and in the absence of a valid FSK signal will decode noise as data. This is not a fault but is due to the wideband properties of noise where sufficient energy may be present within the FSK decoder’s bandwidth. To prevent spurious reception a baseband carrier detect output (DET) is used to determine the validity of the received signal. The detector block is a simple energy detector that receives predominantly in-band energy from a band-pass filter in the device input. The DET should be monitored during reception and used to ‘intelligently’ decide whether the data is likely to valid, suspect or invalid. During periods when there is no data reception the DET will be predominantly low but is likely to false so the receiver should be powersaved where practical. DET does not internally gate the FSK receiver because this would prevent data reception during short duration events such as fades when data recovery may still be possible.
Q. 604 – Are the FX614 and MX614 compatible with the HART specifications? A. Yes they are, the FX614 and MX614 both appear to be suitable for encoding and decoding HART signals but have not been specifically designed to do so. But just to add some further points:
Q. 604 – Does CML offer a suitable replacement device for the TCM3105 (Bell202) modem application? A. CML has several devices that can comply to the Bell202 specification: FX614 / CMX624 / CMX850 / CMX866 / CMX867A / CMX868A an B / CMX869A and B / CMX878. The FX614 is a very popular device which is used as a suitable replacement for the TCM3105. The FX614 offers a cheap and simple solution to wire-line and radio modem applications. Please refer to the following publication for a simple cheap amateur radio solution using the MX614_TCM3105_article
Migration from TDK 73M223 to FX/MX604