Chapter3 HardwareOverview
©NationalInstruments Corporation 3-7 6023E/6024E/6025EUser Manual
Digital I/O
The devices contain eight lines of digital I/O(DIO<0..7>) for
general-purposeuse. You can individually software-configure each line for
eitherinp ut or output. At system startup and reset, the digital I/O ports are
allhigh impedance.
The hardwareup /downcontrol for general-purpose co unters0 and 1 are
connected onboard to DIO6 and DIO7, respectively.Thus, you can use
DIO6 and DIO7 toc ontrol the general-purpose counters. The up/down
control signals are input only and do not affect the operation of the DIO
lines.
♦6025E only
The 6025E deviceuses an 82C55A programmable peri pheralint erfaceto
providean addition al2 4 lines of digital I/O that represent three 8-bit
ports—PA,PB, PC. You can program each port as an input or output port.
The82C55A h ast hree modes of operation—simple I/O (mode 0), strobed
I/O (mode 1), and bidirectional I/O (mode 2). In modes 1 and 2, the three
ports are dividedinto two groups—group A and group B. Each group has
eightdata b its, plus control and status bits from Port C (PC). Modes 1 and
2use handshaking signals from the computer t o synchronize data transfers.
Refert o Chapter 4, Signal Connections, for more detailed information.
Timing Signal Routing
The DAQ-STC chip provides a flexible interface for connecting timing
signalst o other devices or external circuitry. Your device uses the RTSI
bus to interconnect timing signalsb etween devices (PCI and PXI buses
only),and the programmable function input (PFI) pins on the I/O connector
toconnect the device to external circuitry. These connections are d esigned
toenable the device to both co ntrol and be controlled by other devices and
circuits.
Thereare a total of 13 timing signals internal to the DAQ-STC that you can
controlby an external source. You can also control these timing signals by
signalsgenerated internally to the DAQ-STC, and these selections are fully
software-configurable.Figur e 3-4 showsan example of the signal routing
multiplexercontrollin g the CONVERT*signal.