JTECH Communications Inc. SERVALERT200 Manuel D’Utilisation

 

Communication Protocol 
The SmartAlert Transmitter requires, in addition to the correct physical 
interconnection, that the proper RS232 protocol be followed. That protocol is: 
 

•

 1200 

baud 

•

  8 data bits 

•

 No 

parity 

•

  1 stop bit 

 
In addition, the proper message format must be followed. The message format 
descriptions follow. 

While the SmartAlert transmitter does not monitor RTS, it does toggle Clear to 
Send (CTS) to allow it to meter data out of the Host output buffer. Therefore, the 
Host must observe CTS from the transmitter and never send any data while CTS 
is low. Any data sent while CTS is low will be lost! 

The SmartAlert transmitter uses only CTS to indicate when it is OK to send data 
to the unit. The SmartAlert transmitter expects the host will cease sending data 
immediately upon dropping CTS from High to Low. 

 

Some specialized high-speed serial port drivers will buffer up to 16 characters 
and will continue to send data long after CTS has dropped. This causes 
important data to be lost since the SmartAlert transmitter is not paying attention 
to the incoming data while CTS is low. Generally these specialized high-speed 
serial port drivers allow you to set the amount of data that will be buffered and 
therefore sent upon the dropping of CTS. If this is your situation, set this 
parameter to 1 or 0. 

 

 Windows 95 & Windows 3.1X serial port drivers perform as expected and cease 
sending characters immediately upon the transition of CTS from High to Low. 

The RS-232 baud rate required by the SmartAlert transmitter is summarized 
below: 
 

•

  1200,N,8,1 (1200 Baud, No Parity, 8 Data Bits, 1 Stop Bit)