Murata Electronics North America 910M Manual Do Utilizador

 
The modem interface signals on the WIT910 are 3.3-volt signals.  To interface to 5-volt 
signals, the resistor divider network shown below must be placed between the 5-volt 
signal outputs and the WIT910 signal inputs.  The output voltage swing of the WIT910 
3.3-volt signals is sufficient to drive 5-volt logic inputs. 

 
 

2200 

Ω 

 

From 5v 
Output 

 

To 3.3v Input 

4300 

Ω 

 
 
 
 
 
 
 
 
4.2   Evaluation Unit and OEM Module Differences 

 
The evaluation unit has an RS-232 transceiver that translates RS-232 level signals to 3.3-
volt signals for input into the OEM module inside the evaluation unit. A typical 
schematic is shown in Appendix 7.5.  The OEM module does not have any type of RS-
232 transceiver and cannot handle the RS-232 voltages.  This allows the OEM module to 
be easily integrated into any 3.3-volt system without any logic signal translation.  In order 
for the OEM module to function properly several pins need to be driven low or tied to 
ground.  Pin 5 (RTS) and pin 6 (SLEEP) need to be pulled to ground on the 16-pin male 
header.  If you have the OEM module interfaced to an RS-232 transceiver, RTS and DTR 
need to be pulled high on the transceiver side. In the evaluation unit, RTS and DTR are 
pulled high on the transceiver side so the evaluation unit will work with these signals not 
connected.  
 

 
The WIT910 can be operated in a three wire configuration using just TxD, RxD and 
Ground. To operate the WIT910 in this configuration, the Sleep and RTS signals must be 
tied to ground. These signals are pulled up on the WIT910 module and if left 
disconnected will put the radio into sleep mode and RTS will be deasserted. 
 
The WIT910 does not support software flow control (XON/XOFF). Thus when using a 
three wire configuration, there is no flow control. The radio configuration and/or the 
application must insure the transmit and receive buffers do not overflow. The WIT910 
has a 512-byte transmit buffer and a 512-byte receive buffer. For example, the default 
settings for the base slot size and hop duration are 

 and 

 respectively. The 

08H

 

base slot size allows the base to send 32 bytes of data per hop. The 

 hop duration 

provides a 25ms hop dwell time. These default settings provide a base throughput of 19.2 

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