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CHAPTER 8 JTAG BOUNDARY SCAN
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(6) Shift-DR
While the TAP controller is in this state, JDI and JDO are connected according to the current instruction (in
either the boundary scan register or the bypass register). The shift data is shifted, one level at a time, to
the serial output at each rising edge of the signal input to the JCK pin.
When the boundary scan register or bypass register selected with the current instruction is not positioned
in the serial path (when not in the Shift-DR state), the previous state is held. While the TAP controller is in
this state, instruction conversion is not performed.
While the TAP controller is in this state, at a rising edge of the signal input to the JCK pin, the state of the
TAP controller changes as follows:
When the level of the signal being input to the JMS pin is held high: The TAP controller enters the
Exit1-DR state.
When the level of the signal being input to the JMS pin is held low: The TAP controller enters the
Shift-DR state.
(7) Exit1-DR
Exit1-DR is a state that the controller enters temporarily. In this state, at the rising edge of the signal being
input to the JCK pin, if the level of the signal being input to the JMS pin is held high, the TAP controller
enters the Update-DR state. In this way, scan processing is terminated.
On the contrary, at the rising edge of the signal being input to the JCK pin, if the level of the signal being
input to the JMS pin is held low, the TAP controller enters the Pause-DR state.
Regardless of whether the bypass register or boundary scan register is selected with the current
instruction, the previous state is maintained. While the TAP controller is in this state, instruction
conversion is not performed.
(8) Pause-DR
While the TAP controller is in the Pause-DR state, data shift between JDO and JDI, connected to either
the bypass register or boundary scan register, is temporarily halted. These registers, selected with the
current instruction, maintain their previous states.
While the level of the signal being input to the JMS pin is held low, the TAP controller remains in this state.
At the rising edge of the signal being input to the JCK pin, if the level of the signal being input to the JMS
pin is held high, the TAP controller enters the Exit2-DR state. While the TAP controller is in this state,
instruction conversion is not performed.