19
19-6
JTAG
32180 Group User's Manual (Rev.1.0)
19.4 Basic Operation of JTAG
19.4.1 Outline of JTAG Operation
The instruction and data registers basically are accessed in conjunction with the following three operations,
which are performed based on the TAP Controller’s state transition. The TAP Controller changes state accord-
ing to JTMS input, and generates control signals required for operation in each state.
• Capture operation
The result of boundary-scan test or the fixed data defined for each register is sampled. As a register opera-
tion, data input is latched into the shift register stage.
• Shift operation
The register is accessed from outside through the boundary-scan path. The sample value is output to the
outside at the same time data is set from the outside. As a register operation, the bits are shifted right
between each shift register stage.
• Update operation
The data set from the outside during shifting is driven. As a register operation, the value set in the shift
register stage is transferred to the parallel output stage.
The JTAG interface undergoes transition of the internal state depending on JTMS input and on such state
transition, it performs the following two operations. In either case, the operation basically is performed in
order of Capture → Shift → Update.
• IR path sequence
Instruction code is set in the instruction register to select the data register to be operated on in the subse-
quent DR path sequence.
• DR path sequence
The selected data register is operated on to inspect or set data.
19.4 Basic Operation of JTAG
To Next Page
Loading...
Need help?
General
