5I25 2
HARDWARE CONFIGURATION
GENERAL
Hardware setup jumper positions assume that the 5I25 card is oriented in an upright
position, that is, with the PCI connector towards the person doing the configuration.
BREAKOUT POWER OPTION
The 5I25 has the option to supply 5V power from the host computer to the breakout
board. This option is used by all Mesa breakout boards to simplify wiring. The option uses
4 parallel cable signals that are normally used as grounds for supplying 5V to the remote
breakout board (DB25 pins 22,23,24 and 25). These pins are AC bypassed on both the
5I25 and Mesa breakout cards so do not compromise AC signal integrity.
The 5V power option is individually selectable for the two I/O connectors. The
breakout 5V power is protected by per connector PTC devices so will not cause damage
to the 5I25 or system if accidentally shorted. This option should only be enabled for Mesa
breakout boards or boards specifically wired to accept 5V power on DB25 pins 22 through
25. When the option is disabled DB25 pins 22 through 25 are grounded
W1 (P2 POWER ) W2 (P3 POWER)
UP
UP
BREAKOUT POWER ENABLED
DOWN,
DOWN
BREAKOUT POWER DISABLED (DEFAULT)
5V I/O TOLERANCE
The FPGA used on the 5I25 has a 4V absolute maximum input voltage
specification. To allow interfacing with 5V inputs, the 5I25 has bus switches on all I/O pins.
The bus switches work by turning off when the input voltage exceeds a preset threshold.
The 5V I/O tolerance option is the default and should normally be left enabled.
For high speed applications where only 3.3V maximum signals are present and
overshoot clamping is desired, the 5V I/O tolerance option can be disabled. W3 controls
the 5V I/O tolerance option. When W3 is on the default UP position, 5V tolerance mode
is enabled. When W3 is in the DOWN position, 5V tolerance mode is disabled. Note that
W3 controls 5V tolerance on both P2 and P3 I/O connectors.
W3 also selects the pull-up resistor voltage, When 5V I/O tolerance mode is
selected, the I/O pull-up resistors are powered from 5V. When 5V I/O tolerance mode is
disabled, the I/O pull-up resistors are powered with 3.3V.
