B&B Electronics VFG3000 - Manual - Manual (Page 25)

F IELDBUS G ATEWAY M ANAGER B ASICS D OWNLOADING TO A V LINX F IELDBUS G ATEWAY
R EVISION 1 P AGE 9
Note that some caution is required when mounting the CompactFlash card...
• When the card is mounted, the Gateway will periodically inform the PC if data
on the card has been modified. This means that both the PC and the Gateway
will suffer performance hits if the card is mounted during data logging
operations for longer than necessary.
• If you write to the CompactFlash card from your PC, the Gateway will not be
able to access the card until Windows releases its “lock” on the card’s contents.
This may take up to a minute, and will restrict data logging operations during
that time, and prevent access to custom web pages. Fieldbus Gateway Manager
will use the Gateway’s RAM to ensure that no data is lost, but if too many writes
are performed such that the card is kept locked for four minutes or more, data
may discarded. Note that Windows 98 is particularly bad at keeping the card
locked when there is no need for it. Windows 2000 or Windows XP is thus the
operating system of choice when using this feature.
• You should never attempt to use Windows to format a CompactFlash card that
you have mounted via the Gateway, whether it be via Explorer or from the
command prompt. Windows does not correctly lock the card during format
operations, and the format may thus be unreliable and lead to subsequent data
loss. See below for details of how to format a card in a reliable manner.
F ORMATTING THE C OMPACT F LASH
The preferred method of formatting a card is via the Format Flash command on the Link
menu. Selecting this command will explain that the formatting process will destroy all the
data stored on the CompactFlash card and offer you a chance to cancel the operation. If you
elect to continue, the Fieldbus Gateway will be instructed to format the card. Note that this
process may take several minutes for a large card. Slow formats on Gateways that are
performing data logging may therefore result in gaps in the recorded data.
A less attractive method of formatting a card is via a dedicated CompactFlash drive connected
to your PC. If you use this method, be sure to instruct Windows to format the card using
FAT16. For very small or very large cards, Windows will most likely choose the wrong
format by default. Worse still, some versions of Windows Explorer will not allow you to
override the default format, forcing you to use the command line version
FORMAT instead.
S
ENDING THE
T
IME AND
D
ATE
The Link-Send Time command can be used to set the Gateway’s clock to match that of the
PC on which Fieldbus Gateway Manager is executing. Obviously, make sure your clock is
right before you do this!