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MANUAL
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3.1.4 Data Signals Recommended Circuitry
The data group contains six signals, three CMOS inputs from application, two CMOS outputs from phone module,
and one bi-directional signal.
3.1.4.1 TD, RD, CTS, RTS, DTR
All signals are CMOS type.
Figure 20: Data Signal Recommendation
3.1.4.2 VPPFLASH/DCD
This signal, located on pin 23 in the system connector, can be used by the application to enable reprogramming
and data logging of the phone module (service mode). To enter service-mode, the application must have
VCC_MAIN enabled and VPPFLASH/DCD active high when the MODULE_PWR_EN_B pin is set active low. If the
VPPFLASH/DCD signal is left inactive (pulled down in the application) when the MODULE_PWR_EN_B pin is set
active low, the module will start up in normal mode and re-define the VPPFLASH input to a DCD output.
