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Chapter 3 Timing Diagrams
© National Instruments Corporation 3-27 653X User Manual
Figure 3-23.
Trailing Edge Output Handshaking Sequence
Figure 3-24.
Trailing Edge Output State Machine
Reference
Point Action Steps
Initial State ACK is deasserted.
1 The 653X device sends an ACK pulse of programmable width. This indicates
new, valid output data.
2 The peripheral device responds with a REQ pulse. The trailing edge of the REQ
pulse deasserts the ACK signal and requests additional data.
ACK
REQ
2
1
ACK and REQ are shown as active high.
Steps 1-2 are repeated for each transfer.
Initial State
Wait
For
Data
Wait
For
REQ
Programmable
Delay
Programmable
Delay
Wait
For
REQ
When REQ
Unasserted
When 6533 Device has
data to output, output data.*
Clear
ACK
When REQ
Asserted
Initial State: ACK Cleared
Send
ACK
* With REQ-edge latching enabled, the data output is
delayed until the next inactive-going REQ edge.