Debug and Test Interface
14-6
GMS30C7201 Data Sheet
In the descriptions that follow,
TDI
and
TMS
are sampled on the rising edge of
TCK
and
all output transitions on
TDO
occur as a result of the falling edge of
TCK
.
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, whilst new test data is shifted in via the
TDI
pin to the BS
register parallel input latch. In the UPDATE-DR state, the new test data is transferred
into the BS register parallel output latch. Note that 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
EXTEST to ensure that known data is applied to the system logic.
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
TDO
pin, whilst
new data is shifted in via the
TDI
pin to preload the BS register parallel input latch. In
the UPDATE-DR state, the preloaded data is transferred into the BS register parallel
output latch. Note that 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.
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 should be pre-loaded into the boundary-scan register
using the SAMPLE/PRELOAD instruction prior to selecting the CLAMP instruction. In
the CAPTURE-DR state, a logic 0 is captured by the bypass register. In the SHIFT-DR
CLAMPZ
1001
INTEST
1100
IDCODE
1110
BYPASS
1111
Instruction
Binary Code
Table 14-2: Supported Public Instructions