Bird Technologies 4421 - Manual (Page 39)

RS-232 Interface
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Auto Baud
Auto Baud is used to automatically determine the correct transmission rate.
After setting DIP switches 1 through 5, follow the steps below to use auto baud:
1. Set DIP switches 6, 7, and 8 to ON.
2. Connect a controller to the power meter.
3. Turn the power meter on.
4. Send the character U (hexadecimal 55) from the controller to the power
meter.
5. Wait 1 second.
6. If the power meter’s front panel displays LISTEN, the baud rate has been
determined. If not, repeat steps 4 and 5.
If, after 30 seconds, the module cannot absolutely determine a baud rate, it
will choose a rate based on data acquired during the test.
 Note: Auto Baud is the only automatically chosen setting. Other
items such as parity and stop bits must be manually selected.
Talker-Only Mode
The Bird 4421 can be set up for manual operation while automatically sending
data to an output device (Talker-Only Mode). To do so, turn DIP switch 2 OFF
and cycle the power. TALK will be displayed.
In Talker-Only mode, pressing a button on the meter triggers a measurement.
When the measurement is complete, the information is sent to the bus.
Command Syntax
The Bird 4421 accepts two types of commands. General bus commands are
commands, such as Initialize (INT), that apply to any RS-232 interfaced
device. Device-dependent commands are specific to the 4421.
If an invalid command is sent to the unit, an error condition is placed in the
serial poll byte and the offending command is not executed.
A group of device-dependent commands can be sent as a single string as long
as like command categories are not repeated. For example: “PNFCFDT3TRG”.
This string sets up the 4421 to send no prefixes, read forward dBm, make one
reading on “TRG”, and triggers a measurement.
 Note: Commands can be entered in either upper or lower case.
 Note: Only the last command entered of each category will be exe-
cuted. As a command string is processed by the 4421, each category of
command is stored in a separate location. Two commands of the same
category will be stored in the same location, so that the second will
overwrite and erase the first one.
General Bus Commands
The general bus commands supported by the RS-232 interface module are
listed in Table 6-14.
Table 6-14 RS-232 General Bus Commands
Command Effect on Bird 4421
INT Returns to default conditions
ENT Sends a reading to the controller
TRG Triggers reading in T3 mode
B1 to B7 Selects a baud rate
XO/XF Enables/disables software handshake