July 2004
AS91L1006BU
Pass Through Support within the AS91L1006BU Device
The AS91L1006BU device supports a
Pass-Through mode where the primary or master
IEEE1149.1 JTAG signals can be routed to any
one of the LSPs. When this mode is activated, the
“Debug Enable” signal for that LSP will go active,
which can be used to place a processor such as
the MPC8260 into BDM (Background Debug
mode), if required. If no processors are present in
the LSP, the Pass-Through mode can be used to
assist in the generation of the test vectors or
memory tests for the devices that are linked into
the selected LSP. The pass-through feature has
the effect of simplifying the test vector generation
for the LSP, as it also has the effect of removing
the AS91L1006BU device from the test vector
generation process.
PASS_THRU_Enable PASS_THRU_SEL(2) PASS_THRU_SEL(1) PASS_THRU_SEL(0) Active LSP
High
Low
Low
Low
Low
Low
Low
X
X
X
Normal
Operation
Low
Low
Low
Low
High
High
Low
Low
High
High
Low
Low
Low
High
Low
High
Low
High
LSP1
LSP2
LSP3
LSP4
LSP5
LSP6
Table 8 - Pass through mode in AS91L1006BU
ꢁNote: When PASS_THRU_ENABLE is deasserted (logic “1”), then the LSPs are under
control of the AS91L1006BU device logic. When PASS_THRU_ENABLE is asserted (logic
“0”) and if an invalid combination is presented on the PASS_THRU_SEL lines, then all LSPs
are tri-stated.
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