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Chapter 3
Theory of Operation
Digital I/O Circuitry
PC-LPM-16/PnP User Manual
The PC-LPM-16PnP has 16 digital I/O lines that are TTL-compatible.
Pins DIN<0..7> of the I/O connector are digital input lines, and pins
DOUT<0..7> are digital output lines. These lines are monitored or
driven by the Digital Input Register or the Digital Output Register,
respectively. Reading the Digital Input Register returns the current state
of the DIN<0..7> lines. Writing to the Digital Output Register drives
the new value onto the DOUT<0..7> lines. The external device may
drive the EXTINT* signal to indicate the readiness of data transfer.
8
/
I/O RD
8
/
I/O WR
Figure 3-4. Digital I/O Circuitry Block Diagram
8
Digital
/
Input
Register
8
/
Digital
Output
Register
Status
EXTINT*
Register 1
Plug and
Play
Interrupt
Interface
3-8
DIN <0..7>
DOUT<0..7>
National Instruments Corporation
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