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ML674001 Series/ML675001 Series User’s Manual
Chapter 23
JTAG
23-8
23.3.4 Instructions
The instructions supported by the boundary scan function of this LSI are as follows.
The INTEST and
RUNBIST instructions, which are optional instructions in the JTAG standard, are not supported.
Instruction code
Instruction
Register to be selected
IR2
IR1
IR0
EXTEST
Boundary scan register
0
SAMPLE
Boundary scan register
0
1
0
IDCODE
ID register
0
1
BYPASS
Bypass register
1
EXTEST
The EXTEST instruction is used for testing the connection status at board level.
It inputs the output signals of
the boundary scan cells of the device in the previous step into the input boundary scan cells in the Capture-DR
state.
It outputs the data in the output boundary cells to the output pins in the Update-DR state.
Because the core
logic circuit and the boundary scan cells are disconnected, the data that has been input is not transmitted to the
core logic circuit, but is input into the input boundary scan cells.
The data, which has been input into the input
boundary scan cells, can be output from the TDO pin by repeating a shift operation.
SAMPLE
The SAMPLE instruction is used to sample the status of input/output pins during a normal operation.
It inputs
input/output signals into the input and output boundary scan cells in the Capture-DR state.
The data that has
been input is latched inside the boundary scan cells in the Update-DR state.
Unlike the EXTEST instruction,
the core logic circuit and the boundary scan cells are connected in the case of the SAMPLE instruction.
However, the status of input/output data can be sampled during a normal operation via the boundary scan
register, without affecting system operations adversely.
The data, which has been input into the boundary scan
cells, can be output from the TDO pin by repeating a shift operation.
IDCODE
The IDCODE instruction is used to select an ID register in which device information including serial numbers
and parts numbers is stored.
Using this instruction, whether or not correct parts are mounted on the board can
be verified by testing.
The IDCODE of ML674001 series is “0000 0000 0010 0000 0000 0000 0101 1101”.
From MSB, version(000), parts No.(0000 0010 0000 0000), Manufacturer ID(0000 0101 110), 1(fixed value)
The IDCODE of ML675001 series is undefined.
BYPASS
The BYPASS instruction is used to shorten the serial boundary scan chain if it is not necessary to test this LSI
when testing the connection status at board level.
Only the 1-bit BYPASS register is connected between the
TDI and TDO pins.
By setting BYPASS mode, the test data, which has been input to the TDI pin, is output to
the TDO pin without routing through the boundary scan chain.