Agilent Technologies VXI E1439 User Manual
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Using the Agilent E1439
Fiber Optic Interface
Fiber Frames
Data is transmitted over the fiber interface in a series of fiber frames. Each fiber frame is
composed of a series of 32-bit values, which encode to 40 bits. Each 32-bit value can either be
data or an ordered set. Data and ordered sets are strung together to make the three types of fiber
frames—Data Frame, BOF, and EOE. The Data Frame transmits 0 to 512 32-bit data words. The
exact amount of data that is sent depends on the amount of data that is available when the fiber
interface is ready to send the Data Frame. BOF (Beginning Of Frame) is a synchronizing event
that can be sent just prior to the start of data transmission. EOE (End Of Epoch) is a synchronizing
event that contains the last 4 data bytes in an epoch. An epoch is composed of one or more Data
Frames followed by an EOE. The following shows the ordered sets and data that make up the
three fiber frames:
Control Signals
PIO1, PIO2, DIR, and NRDY are FPDP (front panel data port) control signals. These signals can
be defined by another product or you can define their meaning and application.
When an overflow condition in the transmit FIFO occurs, the E1439D asserts FIFO OV indicating
a loss of data. This may occur in
fiber mode if the available fiber bandwidth capability is
exceeded.
If flow control is enabled, the E1439D responds to the STOP and GO signals. See
for details.
Data Frame (Normal Data Fiber Frame)
IDLE
1
1. Pad for Data Frame or BOF
SOF
2
2. Start Of Frame, framing event that embeds PIO1, PIO2, and DIR
0 to 512 data words
3
3. 32 bit or 4 Byte words, maximum 2048 Bytes
CRC
4
4. Cyclic Redundancy Check, optional
FEOF
5
5. Frame End Of Frame, end of Data Frame
SEOF
6
6. Status End Of Frame, embeds FIFO OV and NRDY
GO/STOP
7
7. Flow controls
BOF (Sync Without Data Fiber Frame)
IDLE
1
SOF
2
No data
CRC
4
MEOF
8
8. Mark End Of Frame, end of BOF and EOE
SEOF
6
GO/STOP
7
EOE (Sync with Data Fiber Frame)
SWDV
9
9. Sync With Data Valid, start of EOE
SOF
2
Last 4 data bytes in epoch
10
10.4 bytes, exactly
CRC
4
MEOF
8
SEOF
6
GO/STOP
7