SN75C091A Datasheet, PDF (87/106 Pages) Texas Instruments – SCSI Bus Controller

7.38 timing requirements over recommended operating free-air temperature
and supply voltage ranges
PARAMETER
TEST
CONDITIONS
MIN MAX UNIT
tsu1
Setup time, SDP, SD(0:7) valid before BSY released (high) by
initiator
0
ns
tsu2 Setup time, ATN low before SEL high (see Note 1)
70
ns
See Figure 7–21
td1 Delay time, BSY asserted (low) by target to SEL high
0
ns
Delay time, BSY asserted (low) by target to SDP, SD(0:7)
td2 _invalid
0
ns
7.39 timing characteristics over recommended operating free-air temperature
and supply voltage ranges
PARAMETER
TEST
CONDITIONS
MIN MAX UNIT
Delay time, BSY released (high) by initiator to BSY asserted
td3 _{(low) by target}
CL = 50 pF,
400 650 ns
See Figure 7–21
td4 Delay time, SEL high to start of target mode
150 ns
NOTE 1: This setup time ensures that ATN will be honored by Wait for Select with ATN or Wait for Select without ATN
commands at the completion of the selection phase.
BSY
SEL
Selection
td3
td1
Target
Mode
td4
tsu1
td2
SDP, SD(0:7)
Selection ID Valid
I/O
ATN
tsu2
NOTE: “ - - - - ” waveform for BSY (wired-OR signal) indicates that BSY is being driven by the initiator.
Figure 7–21. SCSI Bus Selection (Target)
7–22