Information Technology Reference
In-Depth Information
Core 2
Core 1
Core 3
Router
Router
Router
Output
Core 4
Core 5
Core 6
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Core 7
Core 8
Output
Core 9
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Core 10
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Router
Fig. 1.
d695 SoC implemented in NoC environment
is used to connect to each I/O pairs. Cores 1 and 9 form an I/O pair. The other
I/O pair consists of core 2 and 6. If core 7 has to be tested by the I/O pair (1,9),
core 1 (source) will feed the test pattern to core 7. The test and response packets
will move through the NoC following a deadlock free deterministic
xy
-routing
technique. Test responses will be collected at core 9 (sink). The solid arrows
indicate the entire routing path. Test and response packets move in pipelined
fashion through this path.
A core supporting preemption, can be scheduled in either preemptive or
non-preemptive manner. As the path to test a core via each I/O pair is fixed,
the path will remain same throughout the test session. Test packets are moved
in a pipelined fashion which can be interrupted, if the core allows preemption.
The preemptive scheduling approaches often result in lower test time than non-
preemptive one, because tests are preempted to avoid resource conflicts that
can create idle time durations in test resources. In preemptive policy, this idle
time can be used to test other cores. The preemptive test strategy does not
significantly increase the ATE's control complexity. It stores the test patterns
in the same way as in non-preemptive strategy, except that the sub-sequences
of test patterns are reordered in ATE memory. The scheduler has to do little
switching between core test and isolation modes.
Test time corresponding to a block of patterns for a core can be calculated
as follows. Let
p
denote the number of test patterns,
l
the maximum scan-chain
length (flit length) and the distances (interms of hops) from source to core and
core to sink be denoted by
h
sₒc
and
h
cₒk
respectively. As each flit is unpacked
in one clock cycle and flits move in pipelined fashion, the time to send test packet
from source to the core plus the time to collect response packet in the sink is
