FUTABA FDL01TU, Instruction Manual

Page: 37 / 83

23
5. Pin 11 can be used as the
hardware reset
. Since the input pin is at high impedance,
never fail to tie the input level.
6. It is no problem if Pins 12, 13 and 14 are leaved open.
7. Since the interface is CMOS structure circuit, it is recommended to take a remedy
against ESD problem (e.g. surge absorber; VRD series, made by Ishizuka Denki).
4.2
Serial Interface Setting
For connecting the FDL01TU modem with an external terminal equipment, RS232C is
appropriate for 1 to 1 topology. And set the
RS485 mode
to make RS485 multi-dropping
topology for multiple equipment connection. Interface configuration can be made with Pin
12
(/RS485ENB ) of the serial communication connector .
To configure the RS485 mode , pull down Pin 12 with 10k ohm register. In this case, do
NOT connect this pin DIRECTLY to the GND. This is because in
RS485 mode
, this pin
will be as an output pin, after the initialization completes, to control the output buffer of the
RS485 driver IC chip. As for the RS232C interface, no connection is required because it is
pulled up inside.
Since the interface level of the FDL01TU modem is CMOS, the level conversion circuit
must be provided outside for connecting it with the RS232C or RS485 interface. For an
example of the level conversion circuit, see p.64
C
ONVERSION
C
IRCUIT
.
Figure 4–1: Connection Example to PC
Converter
PC
RS-232C
FDL modem