National Instruments DIO 6533 - Manual (Page 33)

Chapter 3 Hardware Overview
DIO 6533 User Manual 3-4 © National Instruments Corporation
Figure 3-3. DAQCard-6533 Block Diagram
Unstrobed I/O
The 6533 devices can perform unstrobed I/O, which is basic digital I/O
that employs no handshaking or hardware-controlled timing. You can
write or read data directly to or from the four digital I/O ports of the
6533 devices. The I/O ports contain eight lines each and are labeled A,
B, C, and D. You can configure each line individually for either input
or output.
When you perform only unstrobed I/O, the 6533 device does not require
its handshaking control and status signals to carry timing information.
Therefore, you can use the REQ and STOPTRIG lines as extra data
inputs, and the ACK and PCLK lines as extra data outputs.
DAQ-DIO
Counters
and
Timers
DMA/
Interrupt
Requests
Handshaking
and
Control
Data Latches
and
Drivers
Data Lines
Data Lines
(32)
(16)
PCMCIA
Interface
PCMCIA I/O Channel
20 MHz
Oscillator
Control
Lines (8)
I/O
Connector Clock
Selection
Internal
FIFOs
Bus
Interface
Request
Processing