User's Manual

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4.1 Interface
4.1.1 Pin Assignment
The figure below shows the pin location of the serial communication connector,
following the DCE (Data Communication Equipment) specification.
Figure 4–1: Serial Communication Connector Location
Pin Name Abbreviation I/O Function
1 Carrier Detect Out DCDO output carrier detect output
2 Receive Data RxD output received data output
3 Transmit Data TxD input transmit data input
4 Data Terminal Ready DTR input terminal ready
5 Signal Ground GND – signal ground
6 Data Set Ready DSR output modem ready
7 Request To Send RTS input receive stop/resume request
8 Clear To Send CTS output transmit stop/resume request
9 Carrier Detect In DCDI input ring indicator input
10 Power Supply VCC – 2.7V to 3.3V DC
11 Modem Shutdown POWER_ON input Power On control
12 RS485 Enable 485ENB in/out RS485bus Tx Enable at 485mode
13 Load Default Parameter /INIT input Load default parameter when low
14 Reserved Reserved – Reserved
Table 4–1: Pin Descriptions
1. The serial communication connector’s pin of the modem is defined as the DCE
specification, where transmission indicates input and reception indicates output.
2. Pin 12 is for tri-state control for RS485 driver (CMOS - RS485 level converter) which
will be externally mounted. When the power is turned on or reset, this pin is configured
as an input pin to read the operation mode in the interface. When it is pulled down, the
operation becomes the RS485 mode, and when it is pulled up (or leave open) the
operation becomes the RS232C mode. Since this pin becomes to configure the output
pin after reading the operation mode at the initialize state, never connect it directly to
VCC or GND. This pin is internally pulled up with 470 k ohm.
3. Pin 13 is internally pulled up with 100 k ohm.
4. The input pin tolerates 5 V input (5 V tolerant specification). When the user’s system is
of 5 V, it is possible to interface with a such system.
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