Chapter 5
Signal Timing
DIO 6533 User Manual
5-8
© National Instruments Corporation
8255 Emulation Mode Timing Specifications
Figure 5-7 shows the timing diagram for 8255 emulation mode.
Figure 5-7. 8255 Emulation Timing
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
Data In
tdoa*
tdir
ta*r
tr*r
trr*
trdi
trdo
taa*
tr*a