EV6240 Datasheet, PDF (17/47 Pages) CML Microcircuits – Opto-Isolated serial interface capability

Evaluation Kit for CMX624/CMX644A
EV6240
1.6.1.5
Ring Detection
Modem One Ring detection on the 2-wire line is provided by components C19, C20, R21, R22, R28
and R32, plus D17-D20. The response time is set by components R35 and C27.
Modem Two Ring detection on the 2-wire line is provided by components C31, C32, R49, R50, R56
and R60, plus D30-D33. The response time is set by components R63 and C39.
The evaluation board has been fitted with suitable components for UK applications. See
CMX624/CMX644A data sheets for further details.
1.6.1.6 Ring Stimulus
Ring stimulus can be applied to each Modem via the PIC µC and TR1 (Modem One) or TR3 (Modem
Two). This feature is activated when the user enters the ring stimulus command.
1.6.1.7 IDD Measurement
The evaluation device IDD may be measured for each Modem by removing jumper JP5 (Modem
One) or JP8 (Modem Two) and replacing it with a multimeter.
1.6.1.8
Line Voltage Monitoring
An indication of the level of voltage on the 2-wire lines for each Modem are provided at Bit 0 (Pin 2)
and Bit 1 (Pin3) of the PIC µC Port A. For a 48 Volt dc line the level at this point is ≈ 3.0V dc. These
µC pins can be re-configured as ADC inputs and, with appropriate firmware, be used to monitor the
line voltage. Note that this feature is not used by the current firmware revision.
The line voltage monitoring circuitry can be disabled by removing jumpers, J9 and JP10 (Modem
One) or JP11 and JP12 (Modem Two).
When the line voltage monitoring jumpers (JP9 to JP12) are removed, the line interface will not be
referenced to V_SS.
1.6.1.9
Optional Opto-Isolated Serial Interface.
To avoid potential common mode interference problems when operating over the 2-wire line, the line
interface is referenced to V_SS(line voltage monitoring jumpers fitted).
However, this 2-wire line referencing scheme will cause the line to become unbalanced when the
evaluation kit is connected to a telephone simulator that employs a ground referenced line interface.
Therefore the EV6240 is provided with an optional opto-isolated serial interface to overcome this
problem. The optional interface will also minimise noise from the host PC.
To operate with the opto-isolated serial interface set switch, SW2, to the ‘ISOLATE’ position and
connect a second power supply or battery via the two-way socket, J8. This second power supply
should be set to the same voltage as the on-board regulated supply, (V_DD) either 3.3V or 5V.
1.6.1.10 Serial Interface
On the evaluation board the RS232 DCD (Data Carrier Detect) and DSR (Data Set Read)
handshaking lines are linked to the PC DTR (Data Terminal Ready) line.
For evaluation purposes these handshaking lines are not toggled in the same fashion as a standard
PC Modem. During normal operation and V22/V23 handshaking sequences the PIC µC only uses the
TXD (Transmit Data) and RXD (Receive Data) lines together with the CTS (Clear to Send) and RTS
(Request to Send) handshaking lines to communicate with the PC via the serial interface.
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© 1999 Consumer Microcircuits Limited
UM6240/3