User`s manual

12 PCI-1753 User's Manual
Using Jumpers to Set Ports as Output Ports
By shorting the two pins of the jumpers JPA0, JPB0, JPC0L, JPC0H,
JPA1, JPB1, JPC1L, JPC1H, JPA2, JPB2, JPC2L, JPC2H, JPA3, JPB3,
JPC3L or JPC3H, a user sets the corresponding ports to be output
ports. (JPA0 means jumper for port A0, JPB0 means jumper for port
B0, etc.) Shorting the two pins of a port's jumper disables the port
from being software configurable as an input port. The initial state of
each of these ports after system power on or reset will be logic 0
(voltage low), unless jumper JP1 determines otherwise. (See Jumper
JP1 below.)
Jumper JP1 Restores Ports to Their Condi-
tion Prior to Reset
Jumper JP1 gives the PCI-1753/1753E a new and valuable capability.
With JP1 enabled (i.e., by shorting the lower two pins of JP1), the PCI-
1753/1753E "memorizes" all port I/O settings and output values, and,
in the event of a "hot" reset, the settings and output values present at
the port just prior to reset are restored to each port following reset.
This feature applies to both ports set by software, and to ports
configured as output ports via jumper. Depending on the application,
this capability may allow a card to be reset without requiring a
complete shutdown of processes controlled by the card (since port
values are left unchanged and are interrupted only momentarily).
Complete loss of power to the chip clears chip memory. Thus, even if
JP1 is enabled, if the power to the card is disconnected, the card's
initial power-on state will be the state of an input port with voltage
high input (for software-set ports) or the state of an output port with
voltage low output (for jumper-set ports).
When jumper JP1 is not enabled (i.e., by shorting the upper two pins
of JP1), both power-off and reset results in ports returning to the state
of an input port with voltage high input (for software-set ports) or
returning to the state of output port with voltage low output (for
jumper-set ports).