Manual USB-DIO24-CTR6
6
Functional Description
This USB board is an ideal solution for adding portable, easy-to-install digital I/O and
counter capabilities to any computer with a USB port. The board is a USB 2.0 high speed
device and is fully compatible with USB 3.0 and USB 1.1 ports. The card is plug-and-play
allowing quick connect/disconnect whenever you need additional I/O on your USB port.
The board features 24 bits of CMOS/LVTTL-compatible digital I/O with high-current
capabilities and two 82C54 counter/timers. Each digital port can be programmed to accept
inputs or to drive outputs. Groups of two 8-bit ports and two 4-bit ports are designated as
port A, B, CHi and CLo. Power is supplied to the card via the USB cable. For higher current
sourcing capabilities, external power may be used. The I/O wiring connections are via an
industry standard 50-pin male connector and a variety of optional terminal block adapter
cards. For external circuits, fused +5V (or 3.3V) DC power is available on pin 49 of the
connector. The resettable fuse is rated at 0.5A.
All 24 I/O lines are buffered by a type 74LVC8T245 tristate buffer transceiver capable of
operating in CMOS (+5V) or LVTTL (+3.3V) modes. The mode is set for all pins
simultaneously via an onboard jumper. When using CMOS mode the outputs can sink or
source 32 mA. In LVTTL mode the outputs can sink or source 24mA. The 24 bits are divided
into four ports: two 8-bit ports (Port A, Port B), and two 4-bit ports (Port CLo, Port CHi). Each
port can be configured independently via onboard jumpers for pull-up, pull-down, or no bias.
Each port can also be configured independently, via software command, for use as inputs or
outputs.
The board is available in two models, one with two 8254 counter/timer chips, and one
without. The unit without counters is optimally suited for use with industry standard solid
state module mounting racks. Because this version does not place any counter signals on
pins normally reserved for Ground, it provides a perfectly compatible 50-pin IDC connection.
Unlike most USB digital I/O products which primarily use a human interface device (HID)
driver, we provide an easy to use, Windows-based, custom function driver optimized for
maximum data throughput. This approach exposes the full functionality of the hardware
along with maximizing the advantage of using the high-speed USB 2.0 bus and allows your
application software to achieve up to 4000 transactions per second (compared to 50 or 100
per second typical when using HID drivers).
The board is designed to be used in rugged industrial environments but is small enough to
fit nicely onto any desk or testing station. The board is PC/104 size (3.550 by 3.775 inches)
and ships inside a steel powder-coated enclosure with an anti-skid bottom (4 by 4 by 1.25
inches).
Counter/Timers
On the board are two 82C54 counter chips that each include three 16-bit counter/timers with
each input, output and gate signal buffered, pulled up, and brought to the I/O connector.
They can be connected for use as event counters, frequency output, pulse width, and
frequency measurement.
