RF Neulink NL900PRO - Manual (Page 9)

C H A P T E R 3 - S E R I A L I N T E R F A C E 7
R S 4 8 5 ( 4 - W I R E ) A N D R S 4 2 2
Figure 5 : RS4 85 Full Duplex with T e r m i n at i o n D I P S w i t ch S e t t i n g s
ON ON
1 2 3 4 5 6
1 2 3 4 5 6
With Termination 1 Without Termination
1. Termination is a 120 ohm resistor.
T A B L E 5 : N L 9 0 0 P R O R S 4 2 2 P I N O U T
D B 9 P I N S I G N A L N A M E D E S C R I P T I O N
1 - No Connect
2 T- Serial Data transmitted to radio
9
5
6
1
Female DB9
3 R- Serial Data received by radio
4 - No Connect
5 GND Ground
6 - No Connect
7 R+ Serial Data received by radio
8 T+ Serial Data transmitted to radio
9 Power Optional Power Input 1
1. An internal jumper must be configured in order to use power over Pin 9.
H A R D W A R E F L O W C O N T R O L
Flow control refers to the control of data flow between the host and the NL900-PRO. It is the method used to
handle data in the transmit/receive buffer of the NL900-PRO interface, and determines how data flow
between the host and the NL900-PRO is throttled. Often in serial communication, one device is capable of
sending data much faster than the other can receive. Flow control allows the slower device to tell the faster
device to pause and resume data transmission. (Flow control CTS and RTS are used by the NL900-PRO and
its Host, locally - NOT over the air. Therefore, one NL900-PRO cannot tell the other to slow down or speed
up as is mentioned above in the paragraph).
When the RTS Enable option is selected on the Configuration Utility, the transceivers use hardware flow
control to regulate data flow. While using hardware flow control, the transceiver that is ready to receive
data sends a Clear To Send signal to its host (or the device it is connected to). On the other hand, when a
transceiver has something it wants to send to its host, it checks the state of Ready To Send and if it is logic
low, will send data to its host. If RTS is logic high, it will not send data to its host. These signals are sent
apart from the data itself on separate wires.