Emulation Design Considerations
15-16
15.9.2 Emulation Timing Calculations for SPL
The following examples help you to calculate the emulation timings in the SPL
secondary scan path of your system. For actual target timing parameters, see
the appropriate device data sheets.
Assumptions:
t
su(TTMS)
Target TMS/TDI setup to TCK high
10 ns
t
d(TTDO)
Target TDO delay from TCK low
15 ns
t
d(bufmax)
Target buffer delay, maximum
10 ns
t
d(bufmin)
Target buffer delay, minimum
1 ns
t
(bufskew)
Target buffer skew between two devices
in the same package:
[t
d(bufmax)
– t
d(bufmin)
]
×
0.15
1.35 ns
t
(TCKfactor)
Assume a 40/60 duty cycle clock
0.4
(40%)
Given in the SPL data sheet:
t
d(DTMSmax)
SPL DTMS/DTDO delay from TCK
low, maximum
31 ns
t
su(DTDLmin)
DTDI setup time to SPL TCK
high, minimum
7 ns
t
d(DTCKHmin)
SPL DTCK delay from TCK
high, minimum
2 ns
t
d(DTCKLmax)
SPL DTCK delay from TCK
low, maximum
16 ns
There are two key timing paths to consider in the emulation design:
-
The TCK-to-DTMS/DTDO path, called t
pd(TCK–DTMS)
, and
-
The TCK-to-DTDI path, called t
pd(TCK–DTDI)
.