INSTALLATION
2 - 5
Protected Mode
This mode is active when J3 = PROT.
In Protected Mode, the SSIO-24 responds to a PC power-down or reset
by keeping the OUTPUT modules deactivated. As with Normal Mode,
INPUT modules are not a problem and are not affected by this mode. In
order to sense a reset at the PC, one of the 24 lines from a PIO-XX must
be sacri
Þ
ced. This leaves 23 of the 24 module locations for normal use.
The module location sacri
Þ
ced is KC7. THIS MODE REQUIRES PORT
C/HI TO BE SET FOR OUTPUT ONLY AND MODULE LOCATION
KC7 TO BE UNUSED.
This mode works by sensing the Port C7 line of a PIO-XX board. When
this bit is high, the SSIO-24 is RESET. When this bit is low, the RESET to
the SSIO-24 is removed (NOTE: you must wait a minimum of 200 ms
after removal of the SSIO-24 RESET before enabling the OUTPUT
ports). Whenever the PC resets the PIO-XX board, this bit goes high and
automatically resets the SSIO-24 at the same time the PIO-XX board is
reset. This bit also allows you to quickly shut down the entire SSIO-24
with a single write to this location.
The SSIO-24 has a latch for each of the four (4) ports; the latch disables
OUTPUT modules after a reset. After you reset the SSIO-24 by writing a
one (1) to location C7 of PORT C, you may remove the RESET by
writing a zero (0) to location C7 of PORT C. In order to enable the
OUTPUT modules, you must clear each latch associated with an
OUTPUT port. You may clear the latches by writing zeros to each
OUTPUT port to clear the port and writing ones to the OUTPUT ports
followed by writing zeros to the OUTPUT ports to clear the latch with
the HIGH-to-LOW transition. All OUTPUT ports will now be enabled
(NOTE: you must wait a minimum of 200 ms after removal of the
SSIO-24 reset before enabling the OUTPUT ports).
