Figure 3-12. 8255 emulation output state machine – National Instruments 653X User Manual

Page 67

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Chapter 3

Timing Diagrams

653X User Manual

3-16

ni.com

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

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