Solartron Mobrey 3595 4C, User Manual

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Programming the 3595 4C Interface card 3595 4C User Manual Part One
3-12
35952350 (CH03/AA)
2.
Wait either for the Calendar Grant bit (CGT) to be set, or for the interrupt that indicates this has
happened.
3.
Write the present Host PC operating system time into the calendar registers.
4
. Clear the Calendar Set byte to release access to the calendar.
Once initialised, the calendar and clock can be left to run free at the accuracy determined by the on-card
crystal (error < 2.5 s/day). Alternatively, to synchronise the clock to the PC system clock, a non-zero value
should be written to the Calendar Synchronise byte at the “roll-over” of each second. Note that it is
essential to keep the interval between each write to the Calendar Synchronise byte as close to one second
as possible, so that the phase-locking process can maintain a regular real-time clock.
3.4.6 Selecting IMP devices for polling
By setting the appropriate bits in the Poll Table (Figure 3.4), the Host PC tells the 4C Interface card which
IMP devices are to be polled for data. Throughout the table, each bit represents a specific IMP. Bit 0 of
location 0xC8 through bit 1 of location 0xCE represents IMP 1 through IMP 50, respectively.
0xC9
0xCA
0xCB
0xCC
0xCD
0xCE
0xC8
50
1
9
17
25
33
41
49
Bit 7 Bit 0
Poll Table
(Receive Enable)
Each bit represents a
specific IMP, as indicated
by the IMP numbers.
When a bit is set, the
corresponding IMP is
polled for data.
Figure 3.4: Poll Table
In general, a bit should be set for each IMP from which measurement data is required. (See note on power-
up settling delay below.) Immediately the poll bits are set by the PC, the 4C Interface card begins to poll
the corresponding IMP device(s), checking for data, and reporting communication errors.
The Poll Table set-up can be altered at any time without re-initialising the 4C Interface card. However, once
a bit is set, it should not be cleared unless communication errors occur. Errors may be due, for example, to
IMP removal or ‘not present’.
NOTE: Power-up Settling Delay
After power has been applied to the S-Net, the IMP devices take time to become operational.
For 50V at the IMP, this time could be up to 1 second, whereas for 10V, it is up to 3 seconds.
The voltages quoted are those actually at the IMP, not those applied to the S-Net at the
Controller. The times quoted apply to IMP devices other than the Universal IMP (UIMP): for
UIMP devices, the times should be doubled.
Setting poll bits before the power-up time has elapsed can result in poll errors being generated.
Therefore, it is necessary to delay setting up the Poll Table by a time slightly in excess of the
power-up time.