Xylem H-4191 - Manual (Page 19)

H-4191
SDI-12 Command and Response Protocol 2-9
2.9 Extended Read Flow_Mode and Write Flow_Mode
The RS-232 port of the H-4191 supports optional RTS/CTS hardware flow control for slow host
devices which cannot input or receive the entire SDI-12 response message. The H-419 monitors
it’s CTS input signal and transmits RS-232 characters only if CTS is asserted.
The H-4191 comes from the factory with the RTS/CTS hardware flow control set to OFF. These
two commands allow the hardware flow control feature to be checked or turned ON or OFF. The
On/Off setting is stored in EEPROM internal to the H-4191 and remains in effect even if the
power is lost.
Once a new Flow_Mode value is written, a copy is sent to the sensor data buffer for verification.
This data can be viewed by using a subsequent "D" command. To read or verify the value any
other time, use the "XRFM" command.
Command Response Description
"aXRFM!" “a0011" Read Flow_Mode
"aXWFMn!" “a0011" Write Flow_Mode
Where: a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
XRFM are upper case characters.
XWFM are upper case characters.
n 0 = flow control OFF, 1 = flow control ON
This command takes 001 seconds to complete and places 1 value in the data buffer. Use the
“aD0" command to collect and view the current value.
Example of a H-4191 Extended "Read Flow_Control_Mode" command:
Command
Response Time Values Description
"ZXRFM!" "Z0011" 1 sec 1 Read Flow_Mode
Command Response Description
"ZD0!" "Z+0" Flow Mode = OFF
Example of a H-4191 Extended "Write Flow_Control_Mode" command:
Command
Response Time Values Description
"ZXWFM1!" "Z0011" 1 sec 1 Write Flow_Mode
Command Response Description
"ZD0!" "Z+1" Flow Mode = ON