National Instruments 653X t t t t t, t t t t

Chapter 3 Timing Diagrams
© National Instruments Corporation 3-17 653X User Manual
Figure 3-13. 8255 Emulation Output Timing Diagram
Parameter Description Minimum Maximum
Input Parameters
tr*r REQ low duration 75 —
trr* REQ high duration 75 —
ta*r ACK falling edge to REQ rising edge 0 —
tdir Input data valid to REQ rising edge 0 —
trdi REQ rising edge to input data invalid 10 —
Output Parameters
taa* ACK high duration 100 —
tr*a REQ falling edge to ACK rising edge —150
tdoa* Output data valid to ACK falling edge 25 —
trdo REQ rising edge to output data invalid 100 —
All timing values are in nanoseconds.
REQ
ACK
Data Out Valid
Data In Valid
tdoa*
tdir
ta*r
tr*r trr*
trdi
trdo
taa*
tr*a
ACK and REQ are shown as active low