National Instruments 653X Manuale Utente
Chapter 3
Timing Diagrams
3-16
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Figure 3-12. 8255 Emulation Output State Machine
Wait
For
Data
Wait
For
REQ
Programmable
Delay
Wait
For
REQ
When REQ
Unasserted
When 6533 Device has
data to output, output data.
When REQ
Asserted
Initial State: ACK Cleared
Output Data,
Then Send ACK
Clear ACK