Intel
®
81341 and 81342—Test Logic Unit and Testability
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
1014
Order Number: 315037-002US
20.2.3.2 Instructions
Each of the TAP controller instruction sets is composed of both public and private
instructions. Public instructions are intended for use by purchasers of the part. Since
the instruction set for each TAP controllers is independent of one another, each is listed
separately below
Table 634. TLU TAP Controller Instruction Set
Instruction
Opcode Public/Private
Description
EXTEST
0000000
2
Public
Intended for supporting the boundary-scan feature for testing
device interconnects at the board/system level, the EXTEST
instruction connects only the boundary-scan register between TDI
and TDO in the Shift-DR state. When EXTEST is selected, all output
signal pin values are driven by values shifted into the boundary-
scan register and may change only on the falling-edge of
TCK
in the
Update_DR state.
Also, when extest is selected, all system input pin states must be
loaded into the boundary-scan register on the rising-edge of
TCK
in
the Capture_DR state.
Note:
Data would typically be loaded onto the latched parallel
outputs of boundary-scan shift registers using the SAMPLE/
PRELOAD instruction prior to selection of the EXTEST
instruction.
SAMPLE/
PRELOAD
0000001
2
Public
SAMPLE/PRELOAD performs two functions:
• When the TAP controller is in the Capture-DR state, the sample
instruction occurs on the rising edge of
TCK
and provides a
snapshot of the component’s normal operation without interfering
with that normal operation. The instruction causes Boundary-Scan
register cells associated with outputs to sample the value being
driven by or to the processor.
• When the TAP controller is in the Update-DR state, the preload
instruction occurs on the falling edge of
TCK
. This instruction
causes the transfer of data held in the boundary-scan cells to the
slave register cells. Typically the slave latched data is then applied
to the system outputs by means of the extest instruction.
HIGHZ
0101110
2
Public
HIGHZ puts all output pins into a tri-state mode. When this
instruction is active, the bypass register is connected between
TDI
and
TDO
.
CLAMP
0101111
2
Public
Once the clamp instruction is loaded into the TAP controller
instruction register, the output pins are driven by the parallel output
of the boundary-scan chain. The bypass register is selected as the
serial path between
TDI
and
TDO
when the TAP controller passes
through the Shift-DR state.
IDCODE
1111110
2
Public
IDCODE is used in conjunction with the device identification
register. When selected, IDCODE parallel-loads the hard-wired
identification code (32 bits) into the identification register on the
rising edge of
TCK
following entry into the Capture-DR state. The
instruction selects only the identification register for connection
between
TDI
and
TDO
in the Shift-DR state for serial access.
Note:
The device identification register is not altered by data
being shifted in on
TDI
.
BYPASS
1111111
2
Public
BYPASS selects the bypass register between TDI and TDO while in
Shift-DR state, effectively bypassing the processor’s test logic. 0 is
captured in the Capture-DR state. While this instruction is in effect,
all other test data registers have no effect on the operation of the
system.