Chapter 4
Functional Details
Analog connections
The analog output connections on the PCI-DDA08/12 series are two-wire hookups. One wire connects to the
signal labeled
Vout #
, where # is the channel number from 0 to 7. The other wire connects to the associated
analog ground. The I/O connector pin out is shown in
on page 2-3.
Table 2-2
Analog ranges are software-selectable for ±10 V, ±5 V, ±2.5 V, 0 to 10 V, 0 to 5 V, and 0 to 2.5 V. Each port
may be reconfigured easily and quickly.
Digital connections
The PCI-DDA08/12 emulates two 82C55 chips, but offers much higher drive capability than the 82C55. The
board emulates only Mode 0 of the 82C55 (no strobed I/O or bi-directional I/O bits). The PCI-DDA08/12 is
completely plug-and-play, without any onboard user configurable switches or jumpers.
The 48 CMOS/TTL
compatible digital I/O lines are configured in four banks of eight and four banks of four. You can configure
each bank for input or output.
All of the digital outputs/inputs on the PCI-DDA08/12 connector are TTL-compatible. TTL is an electronics
industry term, short for Transistor Transistor Logic, a standard for digital signals which are either at near 0V or
near 5V. The outputs are capable of sinking 64 mA or sourcing 15 mA. All I/O is brought out to the 100-pin
connector, which also allows connection to the computer's +5 volt and ground.
Unconnected inputs float
Unconnected inputs typically float high, but not reliably. If you are using a PCI-DDA08/12 board for input and
have unconnected inputs, ignore the data from those lines. You do not have to terminate input lines.
Unconnected lines will not affect the performance of connected lines. Ensure that you mask out any
unconnected bits in software.
Pull up and pull down resistors
Whenever the board is powered-on or reset, all ports are set to input mode. To drive all outputs to a known state
after power on or reset, pull all pins either high or low through a 2.2 K
Ω
resistor.
!
The pull-up resistor pulls the input to a high state (+5V). Its resistance of 2200 ohms draws only 2 mA of
the 64 mA available from the output.
!
A 2200 ohm pull-down resistor does the same task, except that the line is pulled low when the board is in
the input mode, and uses only 2 mA of the 15 mA available output provided by the board.
The PCI-DDA08/12 board has open positions for up to six Single Inline Package (SIPs) resistors. The locations
are marked Port 0A, 0B, and 0C, and Port 1A, 1B, and 1C, and are adjacent to the I/O connector. Port 0
n
corresponds to FIRSTPORT
n
, and Port 1
n
corresponds to SECONDPORT
n
.
The SIP resistors provide either pull-up or pull-down action for each eight-line port, depending on their
orientation in the port positions on the board.
The SIP is made up of eight 2.2 K
Ω
resistors. One side of each resistor is connected to a single common point
and brought out to a pin. The common line is marked with a dot or line at one end of the SIP. The remaining
resistor ends are brought out to the other eight pins (refer to
).
Figure 4-1
4-1
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com