National Instruments 653X Manuale Utente
Chapter 3
Timing Diagrams
© National Instruments Corporation
3-17
Figure 3-13. 8255 Emulation Output Timing Diagram
Parameter
Description
Minimum
Maximum
Input Parameters
t
r*r
REQ low duration
75
—
t
rr*
REQ high duration
75
—
t
a*r
ACK falling edge to REQ rising edge
0
—
t
dir
Input data valid to REQ rising edge
0
—
t
rdi
REQ rising edge to input data invalid
10
—
Output Parameters
t
aa*
ACK high duration
100
—
t
r*a
REQ falling edge to ACK rising edge
—
150
t
doa*
Output data valid to ACK falling edge
25
—
t
rdo
REQ rising edge to output data invalid
100
—
All timing values are in nanoseconds.
REQ
ACK
Data Out Valid
Data In Valid
t
doa*
t
dir
t
a*r
t
r*r
t
rr*
t
rdi
t
rdo
t
aa*
t
r*a
ACK and REQ are shown as active low