Bird Technologies 4421 - Manual (Page 28)

Bird 4421 RF Power Meter
16
Serial Polling Enable/Disable (SPE/SPD)
Function Enables or disables the serial polling sequence.
Remarks The SPE command puts all devices in serial poll mode waiting to be addressed.
The SPD command clears the SRQ bit (bit 6) and ends the polling sequence.
When addressed a device sends its status byte to the controller. A value of 1
for a bit means that the device condition that bit refers to is true. A value of 0
means that the condition is false.
The 4421 does not use all bits of the status byte. Table 5-7 lists the bits used,
along with a description and how to reset them.
Table 5-7 IEEE Status Byte Description
CAUTION
During remote operation, periodically monitor the bus service request line.
Failure to detect a service request could result in equipment damage.
Bit Name Condition
6 SRQ Set if a service request is generated by the 4421. If an SRQ
has been received by the controller and this bit is cleared,
other instruments on the bus should be checked to
determine where the SRQ occurred.
Cleared by a serial poll of the 4421.
3 Measurement
Complete Set when the power meter has completed a reading.
Cleared by requesting a reading over the bus.
2 Reading
Underflow Set when the RF power is underrange and a reading has
been completed.
Cleared by requesting a reading over the bus.
1 Reading Overflow Set when the RF power is overrange and a reading has
been completed.
Cleared by requesting a reading over the bus.
0 Error Set if an illegal device-dependent command (IDDC) or
illegal device-dependent command option (IDDCO) was
received, or if the power meter fails the self test.
Cleared by reading the U1 status word. The U1 word
contains details on the error, see “Status” on page 21.