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Figure 3-10. 8255 emulation input state machine – National Instruments 653X User Manual

Page 65

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Chapter 3

Timing Diagrams

653X User Manual

3-14

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Figure 3-10. 8255 Emulation Input State Machine

Wait

For

Space

Wait

For

REQ

Programmable

Delay

Wait

For

REQ

When REQ Unasserted,

Latch Input Data

When 6533 Device has

space for data, input data.

Clear

ACK

When REQ

Asserted

Initial State:

ACK Set

Send

ACK