Evaluation Kit for CMX602B
EV6021
1.6.1.7 Operating Voltage
The operating voltage (VDD) is set to 3.3V. This may be altered by changing components R68 and
R69 which are socketed. To select 5.0Volts set R68 = 620Ω and R69 = 100Ω. The formula for
calculating the values of R68 and R69 is as follows:-
240 (VDD − 1.25)
R68 + R69 =
1.25
Where 240 is the value of R71 in ohms and VDD is the required supply voltage.
1.6.1.8 Clock/Oscillator
The CMX602B may use either an external clock or its own xtal oscillator. A 3.58MHz xtal is provided
on-board for the latter method. Two jumpers JP2 and JP3, which are normally fitted, select the xtal
oscillator. An external clock may be supplied to JP2 pin 2 once the jumpers have been removed.
The PIC16C74A may be provided with an external clock in the same way by removing jumpers JP5
and JP6. Note that PICs programmed by CML are only configured for use with the on-board 4MHz
crystal.
The DTMF generator uses its own 3.58MHz xtal because the xtal oscillator is only operational when
the generator is active and the CMX602B has a 'zero-power' mode (in which its xtal oscillator is
disabled) preventing it from supplying a clock to the DTMF generator.
1.6.1.9 Ring/Line Reversal Detection
Ring/line reversal detection is provided by components C9, C8, R13, R14, R25 and R27 (or R27 in
parallel with R29), plus D2-D5 and TR1. The response time is set by components R33 and C15.
The evaluation board has been fitted with suitable components for UK applications. See CMX602B
data sheet for further details.
1.6.1.10 CMX602B Tone Alert/FSK Receive Path
This part of the CMX602B can be connected directly to the line, via amplifier U2: A, or to the Rx
output of the 2- to 4-wire interface.
When TR2 is conducting the signal from the line is disabled. Alternatively when TR3 is conducting
the signal from the 2- to 4-wire interface is disabled.
Note that if the signal path chosen is via the 2- to 4-wire interface absolute levels at the CMX602B
will depend upon the line impedance of the caller ID simulator in use and on the quality of the
termination of that line. This will have a bearing on tone alert decode and not-decode levels.
1.6.1.11 Handset Connection
A telephone handset can be connected via socket J3. The speaker drive is derived from the Rx
output of the 2- to 4-wire interface and the microphone output is fed to the muteable speech path via
amplifier U1:A and jumper JP1.
1.6.1.12 I
Measurement
DD
The evaluation device I
multimeter.
may be measured by removing jumper JP4 and replacing it with a
DD
1.6.1.13 DTMF Answerback Code
The DTMF answerback (digit D) for the type2 / off-hook / cidcw demonstrations is generated by U5
(National TP5088) and fed to the Tx input of the 2- to 4-wire interface.
2000 Consumer Microcircuits Limited
13
UM6021/4
CMLMICRO [ CML MICROCIRCUITS ]
