Thruline RF Power Meter, Model 4421
13
Figure
8
IEEE Interface Default DIP Switch Settings
Note:
The primary address is used by the control-
ler to refer to specific devices on the bus. When
programming the controller, the address in the
program must be the same as the address set on
the interface module. Each device on the bus must
have a different primary address.
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 1 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 and LISTEN turns on momentarily. A listen-only device on the bus, such as a
printer, can read the value. The power meter is then ready to accept another button press.
Command Syntax
The Bird 4421 accepts two types of commands. General bus commands are commands, such as Device Clear (DCL),
that apply to any IEEE 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 executed. As a command string is pro-
cessed 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 IEEE-488 interface feature are listed in
Table
5
. The syntax for
executing general commands varies among controllers; check the documentation supplied with your controller for
the proper command structure.
Table 5
IEEE-488 General Bus Commands
Command
Effect on Bird 4421
IDN?
Gives product identification
REN
Goes into remote mode when next addressed
GTL
Cancels remote mode, restores local operation
LLO
Locks out local operation
IFC
Goes into talker and listener-idle status
DCL
Returns to default conditions
SDC
Returns to default conditions
GET
Triggers reading in T2 and T3 modes
SPE, SPD
Puts the status byte on the bus
