National Instruments 653 Series User Manual page 68

Chapter 3 Timing Diagrams
When REQ is unasserted,
latch input data.
Wait Wait
Programmable
for for
Delay
REQ Space
When NI 6533 Device has
space for data, input data.
Clear Send
ACK ACK
Wait
When REQ
For
Asserted
REQ
Initial State:
ACK Set
Figure 3-10. 8255-Emulation Input State Machine
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