Boundary-Scan Test Interface
ARM610 Data Sheet
11-4
In the descriptions that follow,
all output transitions on
TDI
occur as a result of the falling edge of
and
TMS
are sampled on the rising edge of
TCK
and
TDO
TCK
.
11.6.1 EXTEST (0000)
The BS (boundary-scan) register is placed in test mode by the EXTEST instruction.
The EXTEST instruction connects the BS register between
TDI
and
TDO
.
When the instruction register is loaded with the EXTEST instruction, all the boundary-
scan cells are placed in their test mode of operation.
In the CAPTURE-DR state, inputs from the system pins and outputs from the
boundary-scan output cells to the system pins are captured by the boundary-scan
cells. In the SHIFT-DR state, the previously captured test data is shifted out of the BS
register via the
TDO
pin, while new test data is shifted in via the
register parallel input latch. In the UPDATE-DR state, the new test data is transferred
into the BS register parallel output latch. This data is applied immediately to the system
logic and system pins. The first EXTEST vector should be clocked into the boundary-
scan register, using the SAMPLE/PRELOAD instruction, prior to selecting INTEST to
ensure that known data is applied to the system logic.
TDI
pin to the BS
11.6.2 SAMPLE/PRELOAD (0011)
The BS (boundary-scan) register is placed in normal (system) mode by the SAMPLE/
PRELOAD instruction.
The SAMPLE/PRELOAD instruction connects the BS register between
TDI
and
TDO
.
When the instruction register is loaded with the SAMPLE/PRELOAD instruction, all the
boundary-scan cells are placed in their normal system mode of operation.
In the CAPTURE-DR state, a snapshot of the signals at the boundary-scan cells is
taken on the rising edge of
TCK
. Normal system operation is unaffected. In the
SHIFT-DR state, the sampled test data is shifted out of the BS register via the
pin, while new data is shifted in via the
TDI
latch. In the UPDATE-DR state, the preloaded data is transferred into the BS register
parallel output latch. This data is not applied to the system logic or system pins while
the SAMPLE/PRELOAD instruction is active. This instruction should be used to
preload the boundary-scan register with known data prior to selecting the INTEST or
EXTEST instructions (see the table below for appropriate guard values to be used for
each boundary-scan cell).
TDO
pin to preload the BS register parallel input
11.6.3 CLAMP (0101)
The CLAMP instruction connects a 1–bit shift register (the BYPASS register) between
TDI
and
TDO
.
When the CLAMP instruction is loaded into the instruction register, the state of all
output signals is defined by the values previously loaded into the boundary-scan
register. A guarding pattern (specified for this device at the end of this section) should
be pre-loaded into the boundary-scan register using the SAMPLE/PRELOAD
instruction prior to selecting the CLAMP instruction.